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A man travels at 4km/h in still water. If the speed of water current is 1 km/h.
It takes 4 hours to reach the place and come back. How far is the place?
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The effective speed traveling downstream is 4 km/h + 1 km/h = 5 km/h;
The effective speed traveling upstream is 4 km/h - 1 km/h = 3 km/h.
Let d be the one way distance, in kilometers.
The travel time downstream is hours; upstream hours.
The total time is 4 hours, giving the "time" equation
+ = 4.
To solve it, multiply both sides by 5*3 = 15. You will get then
3d + 5d = 4*15
8d = 60
d = 60/8 = 7.5 kilometers.
ANSWER. One way distance is 7.5 kilometers.
CHECK. + = 1.5 + 2.5 = 4 hours. ! Correct !
Solved.