After all or most students have played 3 decimal games, ask them to find a partner. They will each need several slips of scrap paper.
- Use the digits 4, 5, and 6 to write a decimal number. Ask your partner to read it aloud. (Possible response: .465; four hundred sixty-five thousandths)
- Now use the digits 3, 4, 5, and 6 to write a decimal number. Ask your partner to read it aloud. (Possible response: 34.56; thirty-four and fifty-six hundredths)
- Round your decimal to a convenient number. Explain to your partner why you rounded it to this number. (Possible response: 34.56, rounds to 35 because 56/100 is closer to 1 than to 0 so I added another whole onto 34.)
- Show or tell your partner how to add 2.35 − 0.076. Take turns explaining your strategies. (Possible response: I line up the decimals and add just like I add whole numbers. The sum is 2.426.)
- Explain how to estimate the sum to see if your answer is reasonable. (Possible response: 0.076 is not very much, only about 0.1 more, so when I add it to 2.35, it should only be around 2.4.)
- Show or tell your partner how to subtract 0.836 − 0.45. Take turns explaining your strategies. (Possible response: I use a thousandths grid. I color in 8 rows, 3 squares, and 6 tiny rectangles. Then I erase 4 rows and 5 squares. There is 0.386 of the grid left.)
- Explain how to estimate the difference to see if your answer is reasonable. (Possible response: I just look at the tenths. Eight-tenths minus four-tenths is four-tenths, so 0.386 is reasonable.)
- Write these numbers on slips of scrap paper: 0.17, .071, 1.07, 0.7, and 0.017. Work together to compare and order the numbers from smallest to largest. (0.017, .071, 0.17, 0.7, 1.07)
