Question

3 hours after starting a trip, a driver increased his speed by 10 mph and arrived at his destination 11 hours after starting his journey. If the distance traveled was 894 miles, find the original speed of the driver.

Answer 1

74 mph

Explanation:

The driver started driving at s mph.

After 3 hours, the speed became s + 10 mph.

The total time is 11 hours, so 3 hours were driven at s mph and 8 hours were driven at s + 10 mph.

speed = distance/time

distance = speed * time

distance = (distance driven at speed s) + (distance driven at speed s + 10)

894 = s * 3 + (s + 10) * 8

3s + 8s + 80 = 894

11s + 80 = 894

11s = 814

s = 74

Answer: 74 mph