* Count the scenery. Have your child keep a running count of items outside the car window, such as brown cows, red cars, or restaurant billboards, and tally the findings. Older children (7 and up) can sharpen their math skills by adding up license-plate numbers or mile markers. For the competitive set: The first one to reach a particular number can be the winner.
* Watch for signals. JoEllyn Mascarenhas of San Diego came up with this colorful graphing activity for her 5-year-old: "I gave him red, yellow, and green dot stickers and drew three columns on a piece of paper," she says. "He used the stickers to mark every traffic light we saw. Later we counted up and compared how many were red, yellow, and green."
* Search for numbers. Challenge your kids to find a specific number on road signs, billboards, or license plates, says Diane Flynn Keith, a mom of two and the author of Carschooling. If your kids like to keep score, make flash cards with numbers on them. They can pull out one card at a time, search for the number on it, and then count how many cards they've piled up by the time you arrive.
* Play with time. A watch with a second hand can be a fun tool. MaryAnna Cashmore, a mom of three in San Francisco, lets her kids share a stopwatch and asks them questions like "How many seconds does it take to breathe in and out ten times?" "How long will it take for our car to go through that tunnel?" And, of course, "How long can we be quiet?"