Question

A boat takes 3 hours more to travel a distance of 30km upstream than it takes to travel the same distance downstream. If the speed of the boat in still water is three times the speed of the stream, then how much time will it take to travel a distance of 180 km in still water? (A) 24 hours (B) 20 hours (C) 25 hours (D) 18 hours ​

Answer 1

Answer:

24 hr

Step-by-step explanation:

Let Speed of boat in still water be u

speed of the stream be v

Distance = Speed * time

A boat takes 3 hours more to travel a distance of 30km upstream than it takes to travel the same distance downstream

$\frac{30}{upstream \: speed} - \frac{30}{downstream \: speed} = 3$

speed of the boat in still water is three times the speed of the stream,

u = 3 v

Downstream speed = u+v =(3v+v)= 4v

upstream Speed = u-v = 2v

$\frac{30}{2v} - \frac{30}{4v} = 3$

$v = \frac{5}{2}$

$u = \frac{5 \times 3}{2}$

Time required to travel 180 km in still water

$= \frac{180}{ \frac{5 \times 3}{2} } = 24 \: hrs$