Question

Curtis rides his bike 9 miles one way then turns around and rides back. On the return trip, his speed is increased 20% because the wind is at his back. Let s be his speed in miles per hour riding against the wind. What is an expression that represents his total time in hours riding there and back?

Answer 1

The expression that represents the total time of his route is "time = 16.5/s".

Explanation:

Curti's ride has two parts, the first one which was made at a speed of "s" and the second one where his speed was 20% higher, therefore "1.2s". The total time to complete this course is the sum of the times for each part, since the average speed is given by:

time = distance/speed

Then the total time for the track is:

time = 9/s + 9/(1.2s)

Using LMC:

time = (1.2*9 + 9)/1.2s = (10.8 + 9)/1.2s = 19.8/(1.2s) = 16.5/s

The expression that represents the total time of his route is "time = 16.5/s".