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?