When I was in middle school, my father learned that he had a very strange autoimmune disorder. His immune system was attacking his liver. In fact, his liver looked like that of a raging alcoholic, which he wasn’t. After months and months of testing and treatments (some pretty ugly), his doctors were finally able to get things under control. But they told us one thing that stuck with me forever: “This isn’t a terminal disease, but it is chronic. As a result, he won’t live as long as he would have if he was healthy.”

To this day, we have absolutely no clue why my father’s immune system turned on him. When I was a toddler, he had surgery to remove part of his thyroid, because it was so overactive. As he aged, he developed other autoimmune disorders, including vitiligo, which caused his skin to lose pigment. But he kept on keeping on.

About seven years ago, his doctors discovered liver cancer. This was a specific kind of cancer, related to his liver disease. They could remove it, but the writing was on the wall: his liver was on its last legs.

So they put him on the liver transplant list. He stopped travelling more than a couple of hours from his hospital. He got poked and prodded. And he waited. And waited.

I’m not sure how many people were on the list at the time. Today, there are nearly 17,000 people waiting for liver donations. Each of these individuals are scored, based on the severity of their liver damage. In 2006, when my father was on the list, the median national waiting time was 321 days. I wasn’t able to find out how many people die before receiving a liver transplant, but it’s estimated that 6,500 people die each year while waiting for a heart, kidney or liver.

After eight months or so of waiting, my family and his doctors got worried. The tumors were coming back and multiplying. He needed a transplant soon. And so I made a decision that changed my life forever. I would donate my liver to him.

The liver is the only organ (besides the skin) that grows back. And a live-donor liver was a great option for someone like my dad. I flew through the medical testing with flying colors.

At about 5:00 a.m. on October 1, 2007, I was wheeled into an operating room at Virginia Commonwealth University Medical Center. They prepped me first, and then brought my father in for the transplant. The entire surgery took at least 8 hours, during which they took one full lobe of my liver and transplanted it into my father. Something like two hours of that time was devoted only to stitching up the large lambda-shaped incision that cut through my abdomen.

After two days of recovery, my father was off the ventilator, and I was walking down the hospital corridors on my own to visit him. Within another two weeks, an MRI showed that my liver had already grown back to about 95% of its original size. (I’m not kidding!) In that time, I had lost around 20 pounds, from not being able to eat for about a week and from the energy my body spent regrowing an organ.

I’m so sad to say that this story does not have a happy ending. I’m perfectly healthy. And my transplanted liver was doing great inside my dad. But no one knew that my father had pulmonary fibrosis. It must have been at the very, very early stages of his disease when he was tested and tested and tested prior to the transplant surgery. The doctors suspect that the progression of the disease was sped up considerably due to massive amounts of oxygen that were pumped into his lungs during surgery and while he was in intensive care.

Had he not had this complication, I have no doubt that he would be living today. He died on November 6, 2007; his liver was still going strong.

My point is not to share a very sad story. My point is to share with everyone some small mathematical facts about organ donation:

1. Each day, about 18 people die, while waiting for a kidney, liver or heart. (That’s 6,500* people per year divided by 365 days.)

2. Right now there are approximately 117,729 people waiting for a kidney, liver or heart. Each year, 4,000 more people join this list.

3. Becoming an organ donor doesn’t have to be as dramatic as my experience was. Most donated organs are from a deceased donor. It takes a split second for you to indicate on your driver’s license that you want to be an organ donor. Or you can sign up at OrganDonor.gov.

4. And happily, most people do not have my father’s experience. As of May 2009, 73.8% of those who had received a transplanted liver were still alive, five years after their surgery. Here are the percentages for others: 69.3% of kidney recipients, 74.9% of heart recipients and 54.4% of lung recipients.

5. It’s not just the big organs that matter. Organs and tissues from a single deceased donor can help up to 50 people. (Yes, 50!) On average 79 people each day receive a donor organ or tissue.

In fact, my father was so convinced of the value of organ donation that even after much of his body failed him, my father was able to donate his eyes, skin and tissue. It is an amazing thought that I and he were able to join together to do this.

So if you haven’t taken the time to indicate that you’d like to donate your organs after death, please do so now. I don’t regret for a moment my gift to my father. At the same time, had there been more deceased donors, it wouldn’t have been necessary.

Talk to your family about organ donation. Get some good information. And at the very least, make an intentional decision one way or the other.

*Earlier, I had a typo here. This number has been corrected.

The post Another Awareness: Organ donations appeared first on Math for Grownups.

Having gone back and forth between the drugstore many times in the last week, I can’t help but wonder how much this whole thing is costing me.

3 cans chicken soup: $1.49 each = $4.47

3 bags Riccola lemon/mint, sugar-free lozenges: $2.05 = $6.15

1 bottle ibuprofen, 80 count: $7.99

1 bottle Delsym 12-hour cough syrup: $11.79

TOTAL: $30.40

At the grocery store today, I bought two bags of oranges for $5. A good night’s sleep is free and so is tap water. Prevention is the cheapest medicine. Lesson learned.

I’ll be back on Friday with a real post — unless I continue to go downhill with this stuff. In the meantime, if you’d like to share your cost-cutting strategies for dealing with or avoiding the common cold, I’m all ears. It’s likely I’ll be reading it at 2:00 this morning, while in the midst of a coughing fit. (Yeah, you should feel sorry for me.)

Oh and if this isn’t enough of a math fix for you, yesterday was Ada Lovelace Day — honoring all of the women who are tops in STEM (science, technology, engineering and mathematics) fields. Share your favorite brainy chick at the Math for Grownups facebook page.

The post More Vitamin C Please appeared first on Math for Grownups.

• More than 3.5 million skin cancers in over two million people are diagnosed annually. That’s more than the combined incidence of cancers of the breast, prostate, lung and colon.
• One in five Americans will develop skin cancer in the course of a lifetime.
• Over the past 31 years, more people have had skin cancer than all other cancers combined.
• Between 40 and 50 percent of Americans who live to age 65 will have skin cancer at least once.
• One person dies of melanoma every 62 minutes.
• One or more blistering sunburns in childhood or adolescence more than double a person’s chances of developing melanoma later in life.
• A person’s risk for melanoma doubles if he or she has had more than five sunburns at any age.

So that’s a lot of numbers and statistics. (Believe me, I only shared a fraction of what I found.) But there are other really important numbers to consider: SPF or sun protection factor.

Basically, SPF is the estimate of time that you can be in the sun without burning. This is really easy math. Let’s assume that without sunscreen, you would burn after 15 minutes. If you used a sunscreen with SPF 15, you’d be able to stay in the sun 15 times as long without burning:

15 minutes • 15 = 225 minutes

225 minutes ÷ 60 = 3.75 hours

If you used a sunscreen with SPF 30, you be able to stay out twice as long:

15 minutes • 30 = 450 minutes

450 minutes ÷ 60 = 7.5 hours

But can you add SPF values? In other words, if you put on SPF 15 and then SPF 30, would you have SPF 45? Mathematically speaking, yes. But in actuality, nope. You’re only as good as the highest SPF you applied.

It’s also important to note that SPF ratings are averages. So while these calculations can help protect you from a nasty burn, you can’t count on them for down-to-the-minute protection. (There’s that imprecision-of-math thing again.)

There are also many, many other variables to consider — including time of day (sun exposure is harshest between 10:00 a.m. and 2:00 p.m.), location (water and sand reflect light, intensifying the rays) and activity levels (sweat and water can cause sunscreen to wear off).

The bottom line? You can do all of the calculating you want, but the only sure-fire way to prevent a sunburn — and the health risks associated with it — is to avoid the sun. Protective clothing can help, along with staying out of the sun when it’s at its strongest. And look for new labeling on sunscreen products. Last summer, the Food and Drug Administration (FDA) introduced new rules for these products, which will start showing up next summer.

This is perhaps the most basic math of all, so there’s no need to make it complicated. For once, you don’t need to multiply or do figures in your head. Just follow these simple rules:

1. Wear the highest reasonable SPF levels. (The FDA says SPF 50 is the best you can do.)

2. Everyone needs sunscreen. All skin types can burn or at least suffer from skin damage. So even if you have dark skin, apply sunscreen.

3. Cover up as much as possible, with broad hats, swim shirts and umbrellas.

4. Avoid the sun at peak times, especially if you plan to be on the water or beach.

5. Reapply sunscreen at least every two hours, more often if you’re sweating or getting in and out of the water.

Simple, eh?

How do you manage the sun and outdoor activities in the summer? If you have cool tips to share, post them in the comments section!

On Monday, we’ll take off on a month of travel math. Got questions? Let me know, and I’ll track down the answers.

The post Feeling the Burn: The math of SPF appeared first on Math for Grownups.

That was yesterday, and today I’m paying for it, big time. Not only do I have a funny-shaped sunburn on my back (from the one cool exercise shirt that I have), but my legs and feet and rear end are screaming: “What the hell??” Still, I know I’ll do this next year, too. Because it’s the one time a year that it’s worth hoisting three bikes on top of our car and driving 15 minutes away to explore the city parks.

Of course, I think about the math involved. Between birdwatching and listening to my almost 12-year-old complaining, what else is there to do? Here’s what I came up with.

1. I woke up yesterday morning with one thing on my mind: I do not want to spend all day on a bike. But would it be all day? Not likely. So I went to the interwebs to help me estimate the time I’d actually be cycling. Here’s what I found:

For the kind of biking I was about to do, an average speed is about 10 miles per hour. I didn’t even bother with a formula; this information was enough to help me estimate that I’d be pedaling for about 90 minutes or so. (I figured I’m slower than average, we’d have one 5-minute break, and we were biking 14 miles, not 10.)

How did I do with my estimate? Not bad. We pushed off at 9:00 a.m. and were munching hamburgers and hotdogs by 11:45 or so.

2. I once thought that the pedals and brakes and chain were the most important parts of the bike. But it turns out that the seat height has more to do with a comfortable ride than most anything else.

Last year, I spent the first half of the course on a seat that was way, way too low. My thighs were burning by the time we hit the rest spot. Luckily, there was a bike tech there who showed me how to adjust my seat and where. I thought I would fall off the precipitous height when he was done, but the rest of the ride was a breeze, comparatively speaking.

Here’s how it works: The leverage of your pedaling is controlled by the seat height. If your seat is too low, you’ll work way, way too hard to get up even the most modest hill. In other words, when your seat is adjusted properly, you’ll get the most efficient pedal stroke. (And your rectus femoris muscle will thank you.)

There are formulas and online calculators that can help you figure this out. But as a once-a-year biker, I rely on a simple idea. When sitting on my bike, I position my feet at 12:00 and 6:00. If my leg is completely extended in the 6:00 position, my seat is at the correct height.

There’s tons more math in cycling, I’m sure. But as a novice, these little calculations and estimates are enough for me. By next year, I’ll forget how sore I am today — and the trouble it is to get our bikes into the rack — and hit these trails again.

Are you a cycler? What math have you used to help keep your pedaling efficient or manage your rides? Share your ideas in the comments section.

Wait! Isn’t it Monday? Where is Math at Work Monday? It’ll be back, I promise. I had some scheduling problems with some sources, so you may see an interview later this week. Don’t worry!

The post Tourin’ Dem Parks: My once-a-year cycling trip appeared first on Math for Grownups.

It’s way too late in the year to start a thru-hike (doing the entire trail), but a section hike would be perfect for a lazy summer day. These are generally less than 5 miles, though you could string together two or more for a weekend adventure. And if you’re nowhere near the Appalachian Trail, just choose another trail to explore.

But how much time should you allot for your hike? This is an important consideration, since it will determine the time you set out (there are no lights on the trail, so once the sun sets, it’s black as pitch) and what you’ll need to bring (food and water are essentials if you’re planning to be gone more than an hour or so).

Experienced hikers can probably gauge how long it will take to hike a given number of miles. But if you’re like me, you don’t have a clue. That’s where pace counting comes in. The length of your stride will tell you how many steps it will take you to go a certain distance. From that, you can get a good estimate of how long it will take you to complete the hike.

To measure the length of your stride, you’ll need two pens, a tape measure and a long hallway or sidewalk. Place one pen at the end of the hallway or sidewalk and stand with your feet together and hells against the pen. Now, walk 10 steps, taking normal strides. After the tenth step, bring your feet together again, and place the second pen behind your heels. Measure the distance between the pens, using the tape measure. Then divide by 10 to find your stride length. Ta-da!

Another method is to estimate your stride based on your height. There’s a simple formula for this, but you’ll first need to have your height converted to centimeters. If you’re a man, multiply your height (in cm) by 0.415; women will multiply by 0.413.

Once you have your stride length, you can use this to estimate the number of strides you’ll take when hiking a particular distance. Let’s say your stride is 28 inches long, and you’re hiking the Chestnut Knobsection in Virginia, which is 2.6 miles round trip. How many steps will you take in that hike?

Ultimately, you’re going to divide the total hike by the length of each stride. But that means you need to have these measurements in the same unit. In other words, you need to convert 2.6 miles to inches. There are 63,360 inches in a mile, so the entire hike is 2.6 • 63,360 or 164,736 inches. Now divide, to find the total number of strides:

164,736 ÷ 28 = 5,883

So on this hike, you’ll be taking a total of 5,883 strides. Still, you don’t know how long the hike will take you, right?

For that step, you need to know how long it takes you to walk a certain number of strides. Let’s go back to the where you found your stride length. If you timed how long it takes you to walk 10 paces, you can easily find the time, right? All you need to do then is use a stopwatch while you take 10 paces. Let’s say that value is 6 seconds. A little bit of math will get you closer to your answer.

First, divide the total paces by 10. Why? Because your time is based on 10 paces, not one.

5,883 ÷ 10 = 588.3

Now multiply this answer by 6 or the number of seconds it takes to walk 10 strides.

588.3 • 6 = 3,529.8

So, it will take you 3,529.8 seconds to hike this section of the trail. It’s probably easier to understand, if you convert this to minutes or hours.

3,529.8 ÷ 60 = 58.83 minutes or just under an hour

Of course this estimate assumes a lot of things: that the terrain is easy to maneuver and that you’re not going to stop to look at the view of Burkes Garden. In other words, you can bet that you’ll be on the trail for longer than an hour, especially if you’re there to metaphorically or literally smell the flowers.

Still, you can use these calculations to estimate the time it will take you to complete any number of hikes. Once you know your stride length and the time it takes for you to walk 10 paces, the math is pretty simple.

What kind of hiking do you love to do? How have you used math to help you plan a hike or other outdoor activity? Share your stories in the comments section.

The post Hittin’ the Trail: Taking the math in stride appeared first on Math for Grownups.

If you’re seen a recent “best college degrees” list, you probably wondered two things: Why the heck is Applied Mathematics on the list, and what is it? First off, applied mathematics is not about crunching numbers. Instead, these folks use higher level mathematics — from abstract algebra to differential equations to statistics — to solve a myriad of problems in a myriad of industries. And that, my friends, is why it’s on the list. In industries like energy, cell phone technology and medicine, math modeling and statistical analysis have been applied to solve really big problems.

Math modeling is one branch of this field that has become a very big deal. Let’s say a city planner wants to know how many snow plows to buy so that the city isn’t paralyzed by a winter storm. Modeling this problem using mathematics is one way to address this problem. The way I look at it, math modeling helps us understand things we can’t see — because they’re part of situations that haven’t occurred or are too far away or are too tiny and hidden.

That too tiny and hidden part that is what math modelers are honing in on with medicine. In this field — sometimes called bioinformatics or computational biology — mathematicians help medical professionals address problems that are under the skin. Here are two examples:

Fighting Cancer: Researchers at University of Miami (UM) and University of Heidelberg in Germany have created a math model that will help oncologists predict how a tumor will grow, and even if and how it will metastasize. There have been other math models that look at tumors, but this one is different. Instead of looking at each cell or all of the cells has a big group, this model creates a kind of patchwork quilt of areas of the tumor to examine. As a result, the doctor can create a tailored plan for treating the disease that is very specific for each patient. The promise is that with specialized (rather than generalized) treatment plans will offer patients a better chance at survival.

Treating Acetaminophen Overdoses: When a patient comes into the emergency room having overdosed on acetaminophen, the ER staff is faced with a really complex decision. Often these patients are hallucinating, unconscious or comatose. And since it’s relatively easy to overdose on the drug (it takes only five times the daily safe dosage, and acetaminophen is in many different over-the-counter and prescription medications), it’s sometimes impossible to determine when and how much of the drug was ingested. There is an antidote, but at a certain point, the doctor needs to skip that step and put the patient on the liver transplant list immediately. The trick is accurately identifying that point. University of Utah mathematician, Fred Adler, developed a set of differential equations that can better pinpoint the critical information needed to make these decisions.

In both of these cases, the math is pretty darned complicated, depending on a branch of calculus called differential equations. This approach is a step up from statistical analysis, which compares patient data to data collected from other patients. In other words, it assumes that tumors grow in the same way in all patients — which we know isn’t true. These dynamical math approaches allow doctors to offer treatments that are customized for each patient, based only on the information collected from the patient.

And the best part is that the doctors don’t have to know the math. If future studies bear out these new discoveries, a simple app can be designed for smart phones or tablets, allowing physicians to make diagnoses and treatment plans bedside.

I suspect these applications will continue to grow, as the medical community turns to mathematicians for insight into what we can’t see. That’s great news, because these advances can save lives.

I hope you’ve enjoyed what we’ve put together here for Math Appreciation Month. If you have questions, please ask them below. I’m always open to ides for future blog posts, so please share them!

The post Saving Lives with Math appeared first on Math for Grownups.

I am not one to talk about my personal weight loss (or gain, usually), especially since I’ve spent years bouncing between feeling good about my figure and avoiding mirrors at all costs.

Fact is, I’ve tried lots and lots of diets — the South Beach Diet, Body for Life, calorie counting, Weight Watchers.  I’ve even tried hypnosis and extreme exercise.  But even though I have never felt completely successful in these attempts, I haven’t failed.  Each time, I’ve refined my goals and figured out things that I will and won’t do.

With all this in mind, I decided in late December that I was going to give Weight Watchers another try. Two things have happened since I was last actively using the program: the PointsPlus program has been refined just a bit, and I wrote a math book.  I have to say that thinking about math so much over the last year has been a great benefit in figuring the PointsPlus values for everything I eat.

(In case you have been living under a rock or don’t know who Jennifer Hudson is, the Weight Watchers program is based on a points system.  Each person is allotted a certain number of points per day, based on their weight and gender.  Everyone also has 49 extra points to eat throughout the week.  Foods have points values based on… well, read on, because that’s kind of what I’m getting to in this post.)

My daily PointsPlus allotment is 26.  I use online tools to help me track the points of the foods that I’m eating (and the drinks that I’m drinking).  And of course, I have those extra 49 points to spread throughout the week.

So first, my math brain figured out that if I use up all 49 points throughout the week (and believe me, I do!), that translates to 7 points per day.  If I only eat an extra 5 points one day, I have an extra 9 points on another day.  (The 49 points carry over, but if I don’t eat all 29 points in a day, poof! they’re gone.)

Believe me, I’ve gotten damn good at these little calculations.  An extra 2 points is the difference between a light and a regular beer.

But it’s the points values themselves that are so amazing, mathematically speaking.  Weight Watchers has done some pretty tricky math to make it easier for us to figure out what to eat.  Instead of counting just calories, we’re considering four components of our food:  protein, fiber, carbohydrates and fat.  These values are run through a formula that outputs a handy-dandy PointsPlus value.  (Online tools and special calculators find PointsPlus values for any foods, and common values are listed in a variety of Weight Watchers resources.)

This formula is pretty complex.  I’ve seen versions of it online, and apparently it is written in black and white in Weight Watcher’s patent.  But I don’t need to have the details to know some pretty simple things:

1.  Four of the formula’s variables are the amount of protein, fiber, carbohydrates and fat in the food.

2.  The answer is likely rounded, since PointsPlus values are all whole numbers.

That last one is pretty important.  It means that 0 points isn’t necessarily 0 points.

You see, almost all veggies and fruits count as 0 points — a big change in the program.  This makes perfect sense, because we should all be eating more fruits and veggies, not deciding between a banana and a low-calorie fruit bar that was made in a factory far, far away.

But fruits and veggies have calories and sugars. That means an apple may actually have 0.2 points (or something like that). So while one apple may be 0 points, 7 apples probably aren’t.  In other words, this is a case of 0 + 0 ≠ 0.

If you’re among the thousands of folks who joined Weight Watchers this month, count math among the skills that will help you lose weight — whether you’re counting your points or trying to make sense of how it all works!

Are you a Weight Watchers member? How have you used math to help you stay on track?  Or if you’ve managed your diet in other ways, how has math helped?  Respond in the comments section.

The post How Many Points Is That? (My weight loss journey) appeared first on Math for Grownups.

You probably also know how easily we can be fooled by diet companies and nutrition labels.  One of those bags of chips you buy at the gas station between errands? The package may claim 250 calories per serving, but the bag may actually contain 2.5 servings.

It’s that tiny little word — per — that screws us up.  It’s so little, you might not even notice it.  But it can make a big difference between reaching your weight goal and wearing a muumuu on the beach this summer.

If you think back to your elementary or middle school math classes, you may remember your teacher explaining that per means each.  And if you think even harder, you might remember the operation (addition, subtraction, multiplication or division) that is indicated by the word per.

Yep, it’s good old division. Think of it this way:

Charlie has six Star Wars figures, and he’s playing with two friends.

“But I want all of them,” he screams. To which you calmly reply, “I know, but that’s not fair. How can we be fair?”

“They can have none, and I can have all of them,” says Charlie, stubbornly.

This is why we teach kids division, you think.

In that situation, you know without a doubt that dividing the Star Wars figures evenly between Charlie and his two friends is not only fair but easy: Because there are six toys and three friends, each friend gets two figures.  In other words, there are two figures per child.

You did that in your head, but the math works out.

6 toys ÷ 3 friends = 2 toys per friend

Now, look more carefully at the above statement.  Toys per friend translates to 6 ÷ 3 or 2, right?  And that means that per means to divide.

Got it?  Good.  Now you can apply this any time you see the word per. In fact, this is precisely what I did on Wednesday, when I was figuring out how long it would take me to lose 25 pounds.

Whatever you expect to lose in a week, the math is simple:

total weight lost goal ÷ loss per week = number of weeks

25 pounds ÷ 1 pounds per week = 25 weeks

So if you think you can lose 2 pounds per week, it’ll take you 12.5 weeks to lose 25 pounds:

25 pounds ÷ 2 pounds per week = 12.5 weeks

Remember, I also wanted to convert the number of weeks to months — because that’s how my brain works:

I already figured out that I can probably reach my goal in 25 weeks.  To find out how many months that is, I can just divide by 4 (the number of full weeks in a month):

25 weeks ÷ 4 weeks per month = 6.25 months

This works for a variety of calculations you may make when embarking on a plan to reach your fitness and weight loss goals.  If your trainer says you should exercise for 5 hours per week, you can divide this in a variety of ways:

5 hours ÷ 5 days = 1 hour per day

5 hours ÷ 4 days = 1.25 hours per day

5 hours ÷ 6 days = 0.83 hours per day (or 50 minutes per day)

And so on.

If you practice this skill, you’ll find yourself doing it all over the place — translating miles per hour to your estimated time of arrival, figuring out how many cheddar cheese goldfish are in a half-serving, calculating the exact number of stickers each of your triplets get from the package, and so on.

So get on with your bad self.  Use per to your advantage and don’t let servings trick you into eating more than you wanted to.

When do you use division (and per) to help with your fitness and weight loss goals?  Share your thoughts in the comments section.

The post One Little Word, One Big Clue appeared first on Math for Grownups.

But I’m not fooling myself.  This is a long process with a lot of little steps, some forwards and a few backwards.  My issue is staying motivated.  I do well for a while, and then I slip up — and eventually give up.  So, I’ve got a good plan that should allow me to make incremental changes and leave lots of room for mistakes.  And to accomplish this, I’ve got both measurable and soft goals.

Sure, I want to eat better (I can count each serving of veggies I eat or glass of water I drink.)  And I want to exercise more.  (I can count my hours at the gym or steps I take from my car to the grocery store.)  But for me, those are big changes that will include a lot of frustrating missteps.  In order to stay focused, the real measurement will be my weight.

My goal is to lose 25 pounds. And I’ll track this by weighing myself once a week.

So how long will it take me to lose the weight? This is where the math comes in.  Here’s what I know:

1. I want to lose a total of 25 pounds.
2. I will probably lose between 0.5 and 2 pounds each week.

Does this mean I’ll be sitting on a beach in a string bikini in August?  (That’s a joke.  I’ve never worn a bikini in my life.)  Let’s look at the math.

A half pound and two pounds is a pretty wide spread, so based on past experience and my inclination to be more conservative, I’m going to estimate that can lose about a pound each week.  So I can reasonably expect to lose all of the weight in 25 weeks.

Whatever you expect to lose in a week, the math is simple:

total weight lost goal ÷ loss per week = number of weeks

25 pounds ÷ 1 pounds per week = 25 weeks

So if you think you can lose 2 pounds per week, it’ll take you 12.5 weeks to lose 25 pounds:

25 pounds ÷ 2 pounds per week = 12.5 weeks

But there’s one more step I need to take.  I don’t think in terms of weeks.  My brain focuses on months. How many months will it take me to lose the weight?

Again, I’m going to estimate.  While there are approximately four weeks in each month, that’s not an exact figure (except in February during a non-leap year).  But since I’m not measuring out medication or figuring out how much to send into the mortgage company or solving problems for my eighth grade math teacher, I don’t have to be exact.  So I’m going to go with four weeks in a month.

I already figured out that I can probably reach my goal in 25 weeks.  To find out how many months that is, I can just divide by 4 (the number of full weeks in a month):

25 weeks ÷ 4 weeks per month = 6.25 months

Ta da!  I can reasonably expect to lose this weight in six months.  That means if all goes well, I should be at my goal by June.

Like me, are you hoping to lose weight in 2012?  Do the math to see when you’re likely to reach your goal.  And if you want to share, feel free in the comments section.  (It’s scary, but you can do it!)Save

The post Watching the Weight Go Down appeared first on Math for Grownups.

Math and cancer?  Turns out the queen of sciences can actually help doctors treat cancer in individual patients.  I looked at a particularly important study by researchers at the University of Miami and University of Heidelberg for Healthymagination, a GE-owned website that addresses health topics.

In short, researchers developed a math model to predict the growth of individual tumors in individual patients.  This is different from previous models that used statistical analysis of how tumors typically grow.  The results also predict whether or not the tumor will metastasize.

The results? Much more reliable diagnoses and treatment plans.  That’s good news for everyone.

Read my guest post here.

Do you have questions about math modeling?  Ask in the comments section.

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