Adjusting numbers in a problem to make mental math easier

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# Adjusting numbers in a problem to make mental math easier - PowerPoint PPT Presentation

COMPATIBLE NUMBERS. Adjusting numbers in a problem to make mental math easier. Example Tell the sum of the following group of numbers. 4 + 9 + 7 + 3 + 11 + 1 + 6. 4 + 9 + 7 + 3 + 11 + 1 + 6. How can we easily add these numbers?. Can you find groups of ten?

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## PowerPoint Slideshow about 'Adjusting numbers in a problem to make mental math easier' - rochelle

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Presentation Transcript

COMPATIBLE NUMBERS

in a problem

to make

mental math

easier

Example

Tell the sum of the following group of numbers.

4 + 9 + 7 + 3 + 11 + 1 + 6

4 + 9 + 7 + 3 + 11 + 1 + 6

How can we easily add these numbers?

Can you find groups of ten?

4 + 9 + 7 + 3 + 11 + 1 + 6

7+3 = 10

6+4 = 10

9+1 = 10

plus 11

Count

10, 20, 30, 40, 41

Can you find groups of ten?

5 + 4 + 12 + 9 + 1 + 6 + 5

9+1 = 10

5+5 = 10

6+4 = 10

plus 12

Count

10, 20, 30, 40, 42

43 +68

40 + 3

60 + 8

43 ~ 40

68 ~ 70

100 + 11

~ 110

Estimate

80

What number is compatible with 79?

65

What number is compatible with 66?

75

What number is compatible with 74?

90

What number is compatible with 92?

85

What number is compatible with 86?

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

Which number sentence best uses compatible numbers to estimate the difference?

• 58 - 39 = 19
• 60 – 40 = 20 C. 68 – 48 = 20
• 55 – 40 = 15 D. 75 – 50 = 25

COMPATIBLE NUMBERS

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

Which number sentence best uses compatible numbers to estimate the sum?

• 88 + 68 = 156
• 90 + 70 =160 C. 95 + 60 = 155
• B. 95 + 65 =160 D. 90 + 65 = 155

Which number sentence best uses compatible numbers to estimate the sum?

• 94 + 61 = 155
• 90 + 70 =10 C. 95 + 60 = 155
• B. 95 + 65 =160 D. 90 + 65 = 155

COMPATIBLE NUMBERS

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