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Published byImogene O’Brien’ Modified over 8 years ago

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Adjusting numbers in a problem in a problem to make to make mental math easier easier

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Example Tell the sum of the following group of numbers. 4 + 9 + 7 + 3 + 11 + 1 + 6

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How can we easily add these numbers?

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Can you find groups of ten? 4 + 9 + 7 + 3 + 11 + 1 + 6 7+3 = 10 6+4 =10 9+1 =10 plus11 Count 10, 20, 30, 40, 41

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Can you find groups of ten? 5 + 4 + 12 + 9 + 1 + 6 + 5 9+1 = 10 5+5 =10 6+4 =10 plus12 Count 10, 20, 30, 40, 42

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43 +68 40 + 3 60 + 8 43 ~ 40 68 ~ 70 100 + 11 ~ 110

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What number is compatible with 79 ? What number is compatible with 66 ? What number is compatible with 74 ? What number is compatible with 92 ? What number is compatible with 86 ? 80 65 75 90 85

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Which number sentence best uses compatible numbers to estimate the difference? 72 – 43 = 29 A. 60 – 50 = 10 B. 70 – 40 = 30 C. 80 – 40 = 40 D. 75 – 50 = 25

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Which number sentence best uses compatible numbers to estimate the difference? 58 - 39 = 19 A.60 – 40 = 20C. 68 – 48 = 20 B.55 – 40 = 15D. 75 – 50 = 25

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Which number sentence best uses compatible numbers to estimate the difference? 76 –39 = 37 A.60 – 50 = 10C. 80 – 40 = 40 B.70 – 40 = 30D. 75 – 50 = 25

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Which number sentence best uses compatible numbers to estimate the sum? 88 + 68 = 156 A. 90 + 70 =160C. 95 + 60 = 155 B. 95 + 65 =160D. 90 + 65 = 155

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Which number sentence best uses compatible numbers to estimate the sum? 94 + 61 = 155 A. 90 + 70 =10 C. 95 + 60 = 155 B. 95 + 65 =160D. 90 + 65 = 155

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Which number sentence best uses compatible numbers to estimate the difference? 78 – 43 = 29 A.60 – 50 = 10C. 80 – 40 = 40 B.70 – 40 = 30D. 75 – 50 = 25

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