Time, Speed & Distance

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A man can row 50 km upstream and 72 km downstream in 9 hours. He can also row 70 km upstream and 90 km downstream in 12 hours. Find the rate of current.


3 km/hr


8 km/hr


4 km/hr


None of these

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Option(D) is correct

Let $x$ and $y$ be the upstream and downstream speed respectively.


\(\dfrac{50}{x}+\dfrac{72}{y}=9\) and


Solving for $x$ and $y$ we get $x=10$ km/hr and $y=18$ km/hr

We know that: 

\(\text{Speed of the stream}\)

\(=\dfrac{1}{2}\times \text{(downstream speed - upstream speed)}\)


4 km/hr

(3) Comment(s)

Chirag Goyal

Wrong Option Marked Please update answer choice.


Another way of solving such type of Questions

Subtract 1st situation from 2nd we've got 20 km upstream and 18 km downstream covered in 3 hrs.(Total)


Using Hit and Trial Method

Let 20 km covered in 2 hrs and 18 km covered in 1 hr.

So Speed in Downstream is 10km/hr.

& Speed in Upstream is 18km/hr.


and Rate of current is ${\dfrac{18-10}{2}} = 4 km/hr.$

Chirag Goyal

Speed in Downstream is 18km/hr.

Speed in Upstream is 10km/hr.


You are saying 4kmph is the answer but then why the answer is marked as 'None of these'