Question

A boat can travel 10km/hr in still water. But upstream it tates 5 times of that time to cover the same distance. What time will the boat take to cover 180 km downstream ?

Answer 1

velocity of boat in still water = 10km/h
let velocity of stream = x km/h
we know velocity = distance/time
let thhe distance be S
BY QUESTION
in still water 10= S/t
=> S= 10t .....................(1)
in upsteam velocity = 10-x
=> 10-x = S/5t
=> S = (10-x)5t .....................(2)
equating (1) and (2)
10t=(10-x)5t
=> x= 8km/h
in downsteam
velocity = 10=8 = 18 km/h
so by velocity=distance/time
18=180/t
=> t=180/18
=> t= 10 hours