Lesson 9: Choosing a Method for Multiplying


Ethan earns $8 an hour babysitting. Would you use mental math to calculate the amount that he earns for any of these times? Which ones and why?

A. 8 hours
B. 10 hours
C. 125 hours


Suzy can walk 87 metres in one minute. Would you estimate or calculate for each?  Why?

A. How far can Mary walk in 9 minutes?
B. Can she walk 500 metres in 6 minutes?
C. Can she walk 500 metres in 7 minutes?

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