SOLUTION: a man walks x km uphill at 3km/h and walks the same distance back at 6km/h. What is his average speed?

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Question 894922: a man walks x km uphill at 3km/h and walks the same distance back at 6km/h. What is his average speed?
Found 2 solutions by Alan3354, richwmiller:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Avg speed = 2*3*6/(3+6)
= 4 km/hr

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
let 's say the man walks 1 hour
r*t=d
3*1=3 km
so he walks 3 km up
so he walks 3 km downhill twice as fast so he takes half the time
6*.5=3
1 hour up and 1/2 hour down=1.5 hr
r=d/t=6/1.5=4 kph
let's say he takes 2 hours uphill
3*2=6
he goes 6 km
going down he goes 6 kph for one hour
6*1=6
r=d/t=12/3=4 kph