# Thrift store prices

Kids love spending their earnings at thrift stores, and I like to encourage them to buy books. At a local thrift store, books cost $5 for 10 books. Ask,

How much is it per book?

“50 cents.”

How do you know?

“I just know.”

How many books do you get for $1?

“Two--oh yeah, two books would be $1, so it would be 50 cents each. 50 cents plus 50 cents is a dollar.”

The way I did it is to take 5/10 which is a half. Half of a dollar is 50 cents.

In this short interplay, while standing in line waiting to pay, we can encourage mathematical thinking by asking not just what, buy why. Often it takes several probing questions to get children to share, but it is worth the effort to get them to explain their reasoning in order to strengthen their logic skills. It will also help them draw mathematical connections to the real world and among different parts of math so that story problems and later proofs in school will be easier. Sharing your strategy shows them alternative and perhaps more efficient ways to get the same answer.