Grades 3-4
The checkout lane of a grocery store can be a good place for children to practice using mental math by estimating the cost of groceries and figuring out change.
What to Do
• As you wait in a grocery checkout lane, use the time to have your child estimate what the total cost of your groceries will be. Tell him that one easy way to estimate a total is to round off numbers. That is, if an item cost 98 cents, round it off to $1. Explain that the answer he gets won't be the exact cost, but it will be about that. Tell him that the word about shows that the amount you say is just an estimate.
• Using the estimated total, ask your child: "If the groceries cost $16 and I have a $20 bill, how much change should the checker give back to me? If the cost is $17.25, what coins is she likely to give me?
• At the checkout counter, ask your child to watch as the items are rung up. What's the actual total cost of the groceries? How does this amount compare to the estimate? When you pay for the items, will you get change back from your $20 bill, or will you have to give the checker more money?
• If you receive change, have your child count it to make sure the amount is correct.
