Question

2 men can swim in stillwater at the rate of 5 km per hour one of them swims downstream through the distance of 2 km and another swim upstream through an equal distance find the difference in the time taken by them if the velocity of the flow of river is 3 km per hour

Answer 1

v1(men)=5km/hr
v2(stream)=3km/hr
v3(upstream)=v1+v2 =5+3=8km/hr
v4(downstream)=v1-v2 =5-3=2km/hr
d=2 km 
t1(time taken by man1)=d/v3=2/8=1/4 hr = 15 min
t2(time taken by man2)=d/v4= 2/2 = 1 hr 
 time difference = 60 min -15min = 45 min