NIFT UG 2016 Question Paper with solutions

Question : 53 of 150

Marks: +1, -0

A man takes 3 hours 45 minutes to row a boat 15 km downstream of a river and 2 hours 30 minutes to cover a distance of 5 km upstream. Find the speed of the river current in km/hr.

1.0 km/hr
1.5 km/hr
1.2 km/hr
1.3 km/hr

Validate

Solution:

Let the speed of the boat = x km/hr and speed of the current = y km/hr
According to the question

\;\;{15}/{x+y}=\;\;{15}/{4}\;\;\;\;\;[∵3\hrs45/60=3{3/4=15/4}\hrs]

⇒x+y=4

....(i)

\;\;{5}/{x-y}=\;\;{5}/{2}

⇒x-y=2

...(ii)
Adding (i) and (ii)

2x=6⇒x=3

and

y=1

Hence, speed of the current = 1 km/hr.

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