Question

A boat goes 16.2 km up stream in 36 min and goes downstream in 28 min. find speed of boat in still water?

Answer 1

Let speed of the boat in still water = x km
Speed of the boat up stream = x - 16.2
Time taken to cover the distance = 36 min = 0.6 hr
So, distance covered in 0.6 hr = 0.6(x-16.2) km/hr
Speed of the boat down stream = x + 16.2
Time taken to cover the distance = 28 min = 0.47 hr
So, distance covered in 0.47 hr = 0.47(x+16.2) km/hr
Since, boat coveres the same distance up stream and down stream,
Therefore,
0.6(x-16.2) = 0.47(x+16.2)
0.6x - 9.72 = 0.47x + 7.614
0.6x - 0.47x = 7.614 + 9.72
0.13x = 17.334
x = 17.334 / 0.13
x = 133.34
which shows that the speed of the boat in still water is 133.3 km.
Hope it will help you. Thanks