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## Chapter 13

### Part 1: Home and School Investigation

Send the Letter to Family (PDF file) home with each child. Once all of the children have brought in the grocery store ads, put them in pairs. Ask children to find the difference in the cost of the two items and to write down how they figured it out. Children can also trade partners and find more differences. You may need to review that ¢ stands for cent and that 1 penny is worth 1¢.

### Part 2: Be an Investigator

A good time to do this investigation is after Lesson 3 on estimating differences.

#### Introducing the Investigation

Tell children they are going to play a game in pairs. Show children the cards you have made from the Investigator Worksheet. Tell children that each child will draw two cards from the deck of cards. Each child will make a prediction of who will get the greater number when they find the difference between the two numbers. Once they make their predictions, the children do the subtraction, check each other's subtraction, and then see who got the greater number. Whoever predicted correctly scores a point. Therefore in each round, both children could score a point, just one of the children could score a point, or neither of the children could score a point. Tell children to keep track of their scores on a separate piece of paper by making a tally mark each time they predicted correctly.

#### Doing the Investigation

Watch children as they play the game. Make sure they understand how to play and are keeping track of the score.