SOLUTION: Ed is a runner and he runs a 8 km loop every day.��The first 4 km, he runs at 12km/hr.��He runs much slower on the way home.��If it takes him 1 hour in total to run the loop, how

Question 1085268: Ed is a runner and he runs a 8 km loop every day.��The first 4 km, he
runs at 12km/hr.��He runs much slower on the way home.��If it takes him 1 hour in total to
run the loop, how fast is he running for the last 4 km?
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
The formula we'll use here is
d = r*t
where,
d = distance
r = rate (aka speed)
t = time

If Ed runs 4 km and his speed is 12 km/hr, then d = 4 and r = 12. Plug these values into the formula above and solve for t
d = r*t
4 = 12*t
4/12 = 12*t/12
1/3 = t
t = 1/3

So it takes Ed 1/3 of an hour, which is (1/3)*60 = 20 minutes to run the 4 km.

20 minutes pass by when Ed runs the first 4 km, leaving 60 - 20 = 40 minutes left over.

40 minutes = 40*(1/60) = 40/60 = 4/6 = 2/3 of an hour

So we'll use t = 2/3 and d = 4 to find the rate (r)

d = r*t
4 = r*(2/3)
3*4 = 3*r*(2/3) ... multiply both sides by 3
12 = 2r
2r = 12
2r/2 = 12/2 ... divide both sides by 2
r = 6

Therefore, Ed's speed on the last four kilometers is 6 km/hr which is the final answer.
RELATED QUESTIONS
A runner runs 80 km per hour after 1 second he was running 90 km per hour what is the... (answered by Lisalovemath,Alan3354)

Zukile walks at 4 km/h and runs 6 km/h.If he turns all the way,he reaches the station 15... (answered by ankor@dixie-net.com)

Alex runs on the track at school each weekday morning. If he runs 5.9 miles each day,... (answered by josgarithmetic,ikleyn,MathTherapy,greenestamps)

Two runners are needed to get some medicine to a village 22 km away. The first runner... (answered by josgarithmetic)

Jim and Derry run a 1.5 mile loop starting at the same time and place. Jim runs an 8.5... (answered by ankor@dixie-net.com)

A man leaves his work at 5:30 PM and heads toward home which is 5 km away. He walks at 5... (answered by josgarithmetic)

on weekends, as part of his exercise routine, Carl goes for a run, partly on paved trails (answered by richwmiller)

If a runner runs at 12 km/h for 5 hours, what was the distance the runner... (answered by london maths tutor)

[ If Eric runs 3/4 of a mile every 8 minutes, how much does he run in one hour? What is... (answered by TimothyLamb)