Nikunj goes 4 kilometres against the current of a stream in 1 hour, and 2 kilometres along the current in 15 minutes. How long will it take him to go 7 kilometres in stationary water?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 1 hour 10 minutes
Given that
Nikunj goes 4 kilometres against the current of a stream in 1 hour
He goes 2 kilometres along the current in 15 minutes
Let the speed of boat and stream be X and Y respectively
According to the question
The downstream speed = X + Y = 2/(1/4) = 8
X + Y = 8 ......(1
The upstream speed = X - Y = 4/1 = 4
X - Y = 4 ....(2
Equation 1 + Equation 2
2X = 12
X = 6 km/h
Hence, the time taken to travel 7 km in still water = 7/6 = 1 hour 10 minutes