Question

John runs for 10 mins at a uniform speed 9kn/h. At what speed should he run for the next 20mins so that theaverage speed comes to 12km/h.

Answer 1

13.5 km/h

Step-by-step explanation:

John runs for 10 min at 9 km/h, then 20 min at v. He will have run a total of 30 min at 12 km/h.

Therefore:

(30 min) (12 km/h) = (10 min) (9 km/h) + (20 min) v

v = 13.5 km/h