Provide an appropriate response.Bridget drives to work at 62 miles per hour before the morning rush hour, but returns home during the evening rush hour at only 40 miles per hour. Explain why 51 is not a valid solution to the problem "What was her average speed for the day's driving?"

Question

What will be an ideal response?

Answer 1

Answers may vary. One possibility: This solution, the average of the two speeds, assumes that the driver is driving at each speed for an equal amount of time. This is an invalid assumption, since it will take the driver longer to drive the same distance at a slower rate (i.e., during the evening rush hour). Thus, the driver will spend more time at the lower speed, and her average speed will be less than 51 mph.