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

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85 – 49 3.

287x – 98x 4.

3 – 2 5.

6 × 39 6.

1.2 ×

174 ÷ 6 8.

9. Volume of the prism = 19m 6 m 2m

396 ÷ 4 10.

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 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 Keep track of how you adjusted the original calculation Find the answer to the original calculation by compensating the answer to the adjusted calculation Find the answer to the original calculation by compensating the answer to the adjusted calculation

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.