Miscellaneous Question 73
- If a boat travels $18$ $ km$ more in downstream than in upstream in 3 hours and if the speed of the boat in still water is $20 $ $km / hr$., find the distance travelled by boat in downstream in 4 hours.
(1) $86$ $ km$.
(2) $92 $ $km$
(3) $68$ $ km$.
(4) $96 $ $km$
(5) None of these
IBPS RRBs Officer CWE (Prelim Exam) 04.08.2019
Show Answer
Correct Answer: 73. (2)
Solution: 73. (2) Let the speed of current be $x$ kmph.
Rate downstream $=(20+x) $ $ \mathrm{kmph}$.
Rate upstream $=(20-x)$ $\mathrm{kmph}$
Distance $=$ speed $\times$ time
$\therefore(20+x) \times 3-(20-x) \times 3=18$
$\Rightarrow 20+x-20+x=\frac{18}{3}=6$
$\Rightarrow 2 x=6 \Rightarrow x=3 $ $\mathrm{kmph}$.
$\therefore$ Rate downstream $=23 $ $\mathrm{kmph}$.
$\therefore$ Distance covered in 4 hours $=$ $23 \times 4=92 $ $\mathrm{km}$
BETA
