Question

A boat travels 30 km upstream in a river in the same period of time as it takes to travel 50 km downstream. If the rate of stream be5km/hr,find the speed of the boat in still water.​

Answer 1

Answer:

20km/hr

Step-by-step explanation:

let speed of boat be x km/hr

and time taken be t hours

now for upstream

x-5=30/t -(1)

for downstream

x+5=50/t -(2)

diving (1) and (2),we get

(x+5)/(x-5)=30/50

5x+25=3x-15

x=20km/hr

Answer 2

Step-by-step explanation:

let speed of boat be x

so speed upstream= (x-5) km/hr

speed downstream= (x+5) km/hr

time taken to travel upstream= d/s

=> 30/x-5

Time taken to travel downstream= 50/x+5

ATQ,

Time taken upstream= time taken downstream

i.e. 30/x-5 = 50/x+5

cross multiply,

30(x+5) = 50(x-5)

30x + 150 = 50x - 250

150 + 250 = 50x - 30x

400 = 20x

400/20 = x

20 = x

So the speed of boat is 20 km/hr .