Question

Sam is training for a 5

km run. While training he runs for 6
minutes, then rests for 2
minutes, runs for 6
minutes, rests for 2
minutes, etc., until he finishes the 5
km. It takes him 26
minutes in total (with the rest periods) to finish the 5
km rum. If Sam runs at a constant speed (when he is not resting), what is this speed in kilometers per hour? (Recall there are 60
minutes in 1
hour.)

Answer 1

15 km/h

Explanation:

How many intervals of running and resting are needed to run and rest for 26 minutes?

Running is in parentheses, resting is not.

Each time he runs (6 minutes) and rests (2 minutes), he takes 8 minutes.

Three times this cycle is 24 minutes. He needs 2 more minutes of running to have a total of 26 minutes.

(6) + 2 + (6) + 2 + (6) + 2 + (2)

Add all the numbers in parentheses which are the times of running.

6 + 6 + 6 + 2 = 20

He ran for 20 minutes and rested for 6 minutes.

He ran 5 km in 20 minutes (of running).

speed = distance/time

speed = [5 km / (20 minutes)] × (60 minutes)/(1 hour)

speed = 15 km/h

Answer: 15 km/h