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.

weredumbmaster22 Mar 11, 2021

#1**+3 **

For AVERAGE SPEED calculations , you have to consider TIME

because km run / TIME = average 'speed'

He needs to average 6 km / hour (his goal)

he has run 2 km @ 12 km/ hr 2km / 12 km/hr = 1 / 6 hr (10 minutes)

he has to run the remaining 8 km in 50 minutes (5/6 hr) 8 km/ (5/6 hr ) = 48/5 km/ hr = 9.6 km / hr

EGAD....I had Anti running a 6k race edited

ElectricPavlov Mar 11, 2021

#4**+2 **

He needs to average 10 km / hour (his goal)

he has run 2 km @ 12 km/ hr 2km / 12 km/hr = 1 / 6 hr (10 minutes)

he has to run the remaining 8 km in 50 minutes (5/6 hr) 8 km/ (5/6 hr ) = 48/5 km/ hr = 9.6 km / hr

ElectricPavlov
Mar 11, 2021

#2**+3 **

At 12K per hour....it takes him 5 min per each kilometer (do you see this ??? )

(Think about it.....there are 12 equal parts in one hour ...so...he runs 2 km in 10 min )

So....he has to cover 10 - 2 = 8 kilometers in 50 remaining minutes = 5/6 hr

So

Rate = Distance / Time

Rate = 8 /( 5/6) = 8 * (6/5) = 48/5 km /hr = 9.6 km/ hr for the rest of the race

CPhill Mar 11, 2021

#3**0 **

I am confused what the answer should be and i typed 4.8 and it was wrong.

weredumbmaster22 Mar 11, 2021