Question

John left the museum and drove south at a rate of 55 mph. Sally left four hours later driving 10 mph faster than John in an effort to catch up to him. How

long did Sally have to drive to catch up with John?
28 hours
22 hours
20 hours
18 hours

Answer 1

22 hours (B)

Explanation:

John's velocity = 55mph

Sally's velocity = 65mph

John's time taken = x

Sally's time taken = x - 4

since they must cover the same distance.

and, distance = vel × time

Sally's vel × time = John's vel × time

55x = 65(x-4)

55x = 65x - 220

-10x = -220

x = 22 hours.

Therefore, Sally catches up after 22 hours