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Two persons P and Q crosses the river st...

Two persons `P` and `Q` crosses the river starting the point `A` on one side to exactly opposite point `B` on the other bank of the river. The person `P` crosses the river in the shortest path. The person `Q` crosses the river in shortest time and walks back to point `B`.Velocity of river is `3 kmph` and speed of each person is `5kmph` w.r.t river. If the two persons reach the point `B` in the same time, then the speed of walk of `Q` is .

A

8kmph

B

12kmph

C

4kmph

D

6kmph

Text Solution

Verified by Experts

The correct Answer is:
B

`t_(p)=(d)/(sqrt(V_(B)^(2)-V_(w)^(2)))=(d)/(sqrt(5^(2)-3^(2)))=(d)/(4)`
`t_(Q)=(d)/(V_(B))=(d)/(5),t_(p)=t_(Q)+Deltat`
`(d)/(4)=(d)/(5)+(x)/(V_(max)), " " x=V_(w)=(d)/(V_(B))`
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