Lesson 9: Choosing a Method for Multiplying

1.

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

2.

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?