3-2-1 Countdown
Kids can practice counting backward as well as forward by using your shopping list — even if they're nowhere near the reading stage. If you write nice and big, and cross o­ items as you toss them into your cart, a child can count the number of objects remaining on the list. My daughter Bella also likes to figure out which is the store's center aisle. We count the aisles, divide the total in half, then count again to the midpoint. Bella gets to pick one item from that aisle as a treat.
Questions to ask: Are there more items in our shopping cart or more remaining on our list? Which aisle will we end up in if we start in aisle 11 and move back three?

Conveying a Rule
When you're finished shopping and get to the checkout, let your child help you put your groceries on the conveyor belt. Sort items according to various rules you both make up. You might start with color, putting the tomato, the strawberries, the apple, and red paper plates together. The green sponge sits alongside the broccoli and the green apple—scented dish detergent. With older kids, move on to more challenging categorization, such as by shape, size, or edible versus inedible.
Questions to ask: What do the broccoli and sponge have in common? How are they different in shape, size, and shade of green? And why is that man with three items in his basket behind us in line fidgeting so impatiently?

Fun Facts Next time you're at a grocery store, see if you notice: Green, brown, and red are the most popular colors of food, and there are almost no naturally blue foods. Source: Infoplease.com.

Shoshana Marchand, a mother of three, has been known to clog up a supermarket aisle while she gives her children an impromptu math lesson. Her writing has appeared on Salon.com and in "Rolling Stone," "Harper 's," and "FamilyFun."