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 must Antti maintain for the last $8$ kilometers of the race? Enter your answer as a number in decimal form, without units. 15 POINTS

Answer 1

Answer:

Speed = distance/time

First 2km:

time = distance/speed

time = (2km) / (12km/hour) = 1/6 hours

Time remaining to get to 1 hour = 1-(1/6) = 5/6 hours

Distance remaining to finish the race = 10km-2km = 8km

speed =  8km/(5/6 hours) = (8*6)/5 = 9.6 km/h

Maintain an average speed of 9.6 km/h

Step-by-step explanation: