Headline Story
Area and Perimeter, #5
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Introduction
Share the Headline Story with the class. Discussion of students’ results may lead to them noticing that the number times itself (for example 8 × 8) is always 1 greater than the product of its neighbors (8 × 8 is 64, but 7 × 9 is 63). There’s good fact practice here, and a useful pattern to remember.
Headline Story
Pick a number (like 9) and square it (multiply it by itself). Then pick its two nearest neighbors (like 8 and 10) and find their product. Compare the two answers. Do this with a few different numbers. What pattern can you find?
Possible student responses
- 9 × 9 = 81 and 8 × 10 = 80
- 5 × 5 = 25 and 4 × 6 = 24
- 7 × 7 = 49 and 6 × 8 = 48
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