Question

Q if rahul rows 15 km upstream in 3 hours and 21 km downstream in 3 hours, then the speed of the stream is?

Answer 1

Rahul rows 15 km upstream in 3 hours


3 hours = 15 km


1 hour = 15/3 = 5 km


Per hour = 5 km


So, Rahul rows 5 km upstream in 1 hour


Rahul rows 21 km downstream in 3 hours


3 hours = 21 km.


1 hour = 21/3 = 7 km


Per hour = 7 km.


So , Rahul rows 7 km downstream in 1 hour .


Let the speed of the stream = x


Let the speed of the boat = y


Form equation -


y - x = 5 -------- (1)


y + x = 7 ---------(2)


Adding (1) and (2) equations


2y = 5 + 7


2y = 12


y = 12/2


y = 6.


substitute value of 'y' in equation 1 .


6 - x = 5


x = 6 - 5


x = 1 .


Speed of the stream = 1 km per hour .


$\bold{Answer: 1 \: km \: per \: hour}$