Vinay rows 1500 m in 1350 seconds against the stream and returns in 15 minutes. What is His rowing speed in still water?

Question

A motor boat goes 10 km upstream and back again to starting point in 55 min.
Find the speed of the motor boat in still water , if stream running at 2 kmph ?

Answer 1

83.33 meter per minute
.
His rowing speed is 83.33 m/min
The stream speed is 16.67 m/min.
.
That means his speed on the first trip is 66.67 m/min => 1500 m in 22.5 min = 1350 sec
And the trip back his speed is 100 m/min => 1500 m in 15 min.
.
-7.5x+37.5y = 3000
-22.5x+22.5y = 1500
-45x+45y=3000
.
(45-37.5)y=(45-7.5)x
7.5y=37.5x
y=5x
3000=(37.5*5-7.5)x
x = 16.67