Headline Story
Attributes of Two-Dimensional Figures, #7
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Introduction
After writing the story on the board, prompt students by asking question such as, “Does the sum have to be a whole number?” and “Do the addends have to be whole numbers?”
Headline Story
A number between 4 and 5 is added to a number between 7 and 8. What can you say about the sum?
Possible student responses
- The sum is between 11 and 13.
- If the two numbers are both closer to the smaller numbers (4 and 7), then the sum is 11 and a little more (4.1 + 7.05 = 11.15; 4.45 + 7.4 = 11.85).
- If the two numbers are both closer to the larger numbers (5 and 8), the sum is 12 and a little more (4.51 + 7.55 = 12.06; 4.9 + 7.96 = 12.86).
- If one number is closer to the smaller number, and the other is closer to the larger, then the sum is closer to 12 than to 11 or 13 (4.1 + 7.55 = 11.65; 4.51 + 7.4 = 11.94).
- The sum could be exactly 12 (7.55 + 4.45 = 12).
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