A man can row 9 1/3 kmph in still water and finds that it takes him thrice as much time to row up than as to… · ABC26GN3823
Subject: General Aptitude · Chapter: Boats and Streams
A man can row $9 \frac{1}{3} \mathrm{kmph}$ in still water and finds that it takes him thrice as much time to row up than as to row down the same distance in the river. The speed of the current is :
(a)$3 \frac{1}{3} \mathrm{km} / \mathrm{hr}$
(b)$3 \frac{1}{9} \mathrm{km} / \mathrm{hr}$
(c)$4 \frac{2}{3} \mathrm{km} / \mathrm{hr}$
(d)$4 \frac{1}{2} \mathrm{km} / \mathrm{hr}$
Answer
Answer (as printed): C
Explanation
Let speed upstream be $x \mathrm{kmph}$. Then, speed downstream $=3 x \mathrm{kmph}$. Speed in still water $=\frac{1}{2}(3 x+x) \mathrm{kmph}=2 x \mathrm{kmph}$. $$\therefore \quad 2 x=\frac{28}{3} \Rightarrow x=\frac{14}{3} .$$ So, Speed upstream $=\frac{14}{3} \mathrm{km} / \mathrm{hr}$; Speed downstream $=14 \mathrm{km} / \mathrm{hr}$. Hence, speed of the current $$\frac{1}{2}\left(14-\frac{14}{3}\right) \mathrm{km} / \mathrm{hr}=\frac{14}{3} \mathrm{km} / \mathrm{hr}=4 \frac{2}{3} \mathrm{km} / \mathrm{hr} .$$