Question

In a stream whose current flows at the speed of 3 km/hr, a man rowed upstream
and returned to his starting point in 6.25 hours. If the man rows at a speed of
5 km/hr, in still water, how long did he row upstream?​

Answer 1

Answer:

Upstream :

time = t hrs ; rate = 5-3 km/h ; distance = 2t km

Downstream:

time = 6.25-t hrs ; rate = 5+3 km/h ; distance = 8(6.25-t) km

up stream distance = down stream distance

2t = 8(6.25-t)

10t = 50

t = 5 hr (time to row upstream)

Answer 2

Answer:

Upstream distance=Downstream distance = x

Speed of boat (b) = 5 Km/hr

Speed of stream (s)= 3 Km/hr

Time taken to travel upstream and downstream (x + x = 2x) = 6.25 hrs

time= distance / speed

Speed of boat during upstream = b-s

Speed of boat during downstream = b+s

x / (b -s) + x / (b + s) = 6.25

On solving you get x= 10

Upstream distance=Downstream distance = 10 km

Time taken to row upstream : t=10/(b-s) = 10 / 2 = 5 hrs

Happy learning!

Step-by-step explanation: