s/w engineer

A software engineer starts from home at 3pm for evening walk. He walkspeed of 4kmph on level ground and then at a Speed of 3kmph on the uphill and then downhill at a speed of 6kmph to the level ground and then at a speed of 4kmph to the Home at 9pm.
what is the distance on one way?

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Since time uphill is twice the time downhill but distance is the same

Calculate the average speed for time spent walking up then down
U - Time spent walking up hill
P - Time spent going down hill
U = 2P

distance walked uphill then down
3kmph * U + 6kmph * P
3kmph * 2P + 6kmph * P
6kmph * 2P
12kmph * P

Time spent walking up then down
U + P = 2P + P = 3P

Average speed for the uphill then downhill
Distance / Time

(12kmph * P) / 3P

Thus he average 4kmph for the trip of 6 hours regardless of the distance walked Level, Uphill or Downhill
so he walked 24 km

There are too many variables to solve this riddle, or important information is missing ...

Does he take the same road back ?
How far does he go uphill/downhill ?
shilpi84Author Commented:
yes he takes the same road back and rest i dont know.we will have 2 take average speed?
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You can't take the average speed if you don't know what part of the distance was uphill.

If the distance uphill is the same as the distance between his home and the hill, then here's the solution :

(((4 + 3 + 6 + 4) / 4) * 6) / 2

Or :

12,75 km
Ignore my solution !!! It's wrong !! mlmcc's solution is the correct one !
I had the same thought at first until I tried an example and it came out at 24 km.

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