Question

Kevin drove to the mountains last weekend. There was heavy traffic on the way there, and the trip took 9 hoursWhen Kevin drove home, there was no traffic and the trip only took 4 hours. his average rate was 40 per hour faster on the trip home, how far away does Kevin live from the mountains? Do not do any rounding

Answer 1

288 miles

Explanation:

Kevin's trip took 9 hours one way, and 4 hours the other way, driving 40 mph faster. You want to know the one-way length of Kevin's trip to the mountains.

Setup

The relation between time, speed, and distance is ...

speed = distance/time

Using d to represent the one-way distance Kevin drove, we can relate his speeds with ...

d/4 = 40 +d/9 . . . . . . speed coming home was 40 mph more than going

Solution

Multiplying by 36 to clear fractions, we have ...

9d = 1440 +4d

5d = 1440 . . . . . . . subtract 4d

d = 288 . . . . . . . divide by 5

Kevin lived 288 miles from the mountains.