Whether you’re flying across country or crammed in the mini-van for a trip to Grandma’s house, keeping a kid occupied on a long trip may mean you need a vacation at the end of it. And sure, we can plug them into movies or iPods or video games, but is that really what you want your children to remember about their trip to the Grand Canyon?

Being trapped in a car or plane or train for hours at a time will either kill you or make you stronger, and I’m rooting for stronger. You can look at this as an opportunity to hang out with your kids — and even sneak in a little math.

I know that sounds really, really geeky, but this was a real, live question that a parent asked me over at MSN.com’s Mom’s Homeroom where I’m the resident math expert. Since we’re talking travel this month, I thought I’d expand on the ideas here. The parent asked: “What are some fun math games that I can play with my 10 year old son and 7 year old daughter while on road trips?”

First and Last

This is a take on a game that I used to play with my daughter. She would say a letter, and I would say a word that began with that letter. Then she would identify the last letter of that word, and give me a word that began with that letter. For example: S prompted me to say spaghetti. She would say I and then igloo.

This can easily be adapted to math, which helps kids (and adults) practice their mental computation skills. For example:

First player: 16 + 3

Second player: 19

Second player: 19 – 10

First player: 9

First player: 9 • 3

and so on…

Set the rules of the game so that everyone can play. For example, no negative numbers, fractions or exponents, if your 13 year old is playing with his 8-year-old brother. Or tell them that they can only use even numbers or only addition and division. You might just find that your kids are getting really creative — and making some cool connections. (Did you know that when you add or subtract only even numbers, the answers will always be even?)

If you’re in the car, sometimes the only thing to read are road signs and license plates. But if you take a close look, you could find some math in there. In fact, someone has created a cool wiki devoted to this game. Take a look at the sign below.

Do you see the math in there? It’s a very simple addition problem: 2 + 4 = 6.

These can get downright complex! But you can keep it easy for your younger kids. Look out for route numbers, license plates and billboards for more ideas. If you’re used to traveling the same road over and over, this is a particularly good way to pass the time. What’s old becomes new again!

I Spy

This perennial favorite can be adapted to all sorts of situations. For example:

“I spy with my little eye: a prime number!”

“I spy with my little eye: 17!”

I spy with my little eye: a fraction!”

Try this with a boring magazine on the plane. Keep the questions on grade level and offer encouragement for good — or close or creative — answers. Need to remember what a prime number is? If you’re not driving, do a quick search on your smart phone.

There are countless other ideas that can help you pass the time and inject a little math into the trip. Do you have suggestions? Offer them in the comments section!