A motor boat covers the distance between the two sponts on the river 9h and 13 h downsream and upstream respectively. find the time required by the boat to cover this distance in still water.
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Let speed of still water be u km/hr and speed of stream be v km /hr.
Let the distance to be covered be x km.
Time taken while travelling downstream = x/ u+v = 9 h ..... (1)
Time taken while travelling upstream = x/ u-v = 13 h ...... (2)
Dividing (1) and (2)
u-v/u+v = 9/13
13u - 13v = 9u + 9v
4u = 22v
v = 2u/11
Substituting for v in (1)
11x / 13u = 9
x = 117u /11
Time taken to cover x distance in still water
= x/u = 117/11 hrs = 10.6 hrs
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