Question

40. A man can swim in still water at a speed of 4
kmph. He desires to cross a river flowing at a
speed of 3 kmph in the shortest time interval
If the width of the river is 3km time taken to
cross the river (in hours) and the horizontal
distance travelled (in km) are respectively
3
39
1 15
1)
2)
3) 4)
4 4
دیا
7​

Answer 1

Answer:

Since he makes his strokes normal to the river current, the movement of the river will have no effect on the time of crossing the bank.

The time will be, T=

Speed

Distance

=

4

1

hr=0.25hr=15min.

In the same time, he will go down by

Distance=Speed x time=3km/hr x 0.25hr=0.75km=750m