Question

A man can swim with a speed of 4.0 km/h in still water. How long does it take to cross a river of 1.0 km wide if the river flows steadily at 3.0 km/h and he makes his strokes normal to the river current? How far down the river does he go when he reaches the other bank?

Answer 1

Hii dear,

# Answer-
t = 15 min
s = 750 m

## Explaination-
# Given-
speed of man vm = 4 km/h
speed of river vr = 3km/h
width of river l = 1 km

# Solution-
Time taken to reach other bank,
t = l/vm
t = 1/4
t = 0.25 h = 15 min

Distance covered down the river,
s = vr×t
s = 3×0.25
s = 0.75 km = 750 min

Hence, Time taken to reach other bank is 15 min and distance covered down the river is 750 m.

Hope that is helpful...

Answer 2

Given :

Let t be the time taken to cross the river

width of river=1km

speed of man=4km/h

speed of river=vr=3km/h

Speed= distance/ time

Time= distance/ speed

Time= width of river/ speed of man = 1/4 h= 15min

Distance moved along the river in time=t=Vrxt

= 3kmx1/4= 0.75km=0.75x1000=750m

∴ The man goes 750m down the river when he reaches the other bank.