After students play Three in a Row, discuss the strategies they used to choose their factors.
- Who would like to show how to estimate the product of 109 × 49.3? (Possible response: 109 is close to 100 and 49.3 is close to 50. 100 × 50 = 5000. 1 × 5 is 5, and then I added 3 zeros.)
- How much larger is 5000 than 50? (5000 is 100 times larger than 50.)
- Show how to multiply 100 × 49.3. Explain how you placed the decimal point in the answer. (Possible response: To make 49.3 100 times larger, I can move the decimal point in 49.3 two places to the right, 4930.)
- How much smaller is 50 than 5000? (50 is one-hundredth of 5000 or 50 is 100 times smaller than 5000.)
- Who would like to show how to estimate the product of 109 × 0.01? (Possible response: One-hundredth of 100 is 1. Or, 100 times 1/100 is 100/100 or 1.)
- Show how to multiply 109 × 0.01. Explain how you placed the decimal in your answer. (Possible response: I just looked at the whole numbers and multiplied 109 × 1. Then I counted the number of places behind the decimal points in the factors, which is 2, and then made sure my answer had that many numbers after its decimal point. The product is 1.09.)
