Question

Antti entered a 10-kilometer race. His goal is to finish in one hour. He starts off sprinting and completes the first 2 kilometers of the race at an average speed of 12 kilometers per hour. To achieve his goal of a one-hour finish time, what average speed (in kilometers per hour) must Antti maintain for the last 8 kilometers of the race? Enter your answer as a number in decimal form, without units.

Answer 1

12 km/hr = 12 km/60 min= 2 km/10 min

so, first 2 km take 10 min. so, she is left with 50 min and a distance of 8 km

so, required speed = 8km/50min=8*60/50 kmph =9.6 kmph.