Mental Math

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Mental Math

• Do not copy the question and express your answer
  only on your page.
• Be prepared to discuss strategies at the end.

2
Get Ready
3
99 38

• 1.

4
5.98 2.31

• 2.

5
85 49

• 3.

6
287x 98x

• 4.

7
3 2

• 5.

8
6 39

• 6.

9
1.2 1.9

• 7.

10
174 6

• 8.

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9. Volume of the prism
2m
6 m
19m
12
396 4

• 10.

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Compensation Strategy

• When you might use this technique
•   Use this technique when a calculation can be
  chosen that is close to the original one and that
  is easy to do mentally
• How to Use this Technique
• Change the original calculation to one that is
  easy to do mentally.  Changing only one number
  usually makes the adjustment at the end easier
•    Keep track of how you adjusted the original
  calculation
•    Find the answer to the original calculation by
  compensating the answer to the adjusted
  calculation

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• How does the compensation strategy relate to the
  two big principals of mental math ?
• You usually adjust a number to a multiple of a
  power of ten making it easier to work with.
• and/or
• You usually start to work with the highest place
  values.