Question

Michel started to drive from New York to Washington, DC, which is 120 miles away, at 7:00 AM. For the first hour and a half of her trip, Michel was driving at a speed of 50 mph. What was her average speed during the second part of the trip, if she reached Washington at 10:00 AM?

Answer 1

The average speed on the second part was 30 mph.

Explanation:

The whole trip between New York and Washington is 120 miles. On the first part he drove at 50 mph for 1.5 h, from 7 AM to 8:30 AM, therefore he drove a distance of:

distance = speed*time = 50*1.5 = 75 miles

So the second part had a length of 120 - 75 = 45 miles. With an elapsed time of 1.5h, therefore the average speed was:

speed = distance / time

speed = 45 / 1.5

speed = 30 mph

The average speed on the second part was 30 mph.