Miscellaneous Question 86
- A boat running downstream takes 240 minutes to cover a certain distance and it takes 528 minutes to cover the same distance running upstream. What is the ratio between the speed of the boat in still water and speed of the water current respectively?
(1) $4: 1$
(2) $5: 2$
(3) $8: 3$
(4) $6: 5$
(5) $3: 1$
(IBPS RRBs Officer Scale-I CWE Main Exam, 13.10.2019)
Show Answer
Correct Answer: 86. (3)
Solution: 86. (3) Speed of boat in still water $=\mathrm{b} $ $\mathrm{km} / \mathrm{min}$. and speed of current $=\mathrm{c}$ $ \mathrm{km} /$ minute
$\therefore$ Rate upstream $=(\mathrm{b}-\mathrm{c}) $ $\mathrm{km} /$ minute
$\therefore$ Rate downstream
$=(\mathrm{b}+\mathrm{c}) $ $\mathrm{km} /$ minute
$\therefore(\mathrm{b}-\mathrm{c}) \times 528=(\mathrm{b}+\mathrm{c}) \times 240$
$\Rightarrow(\mathrm{b}-\mathrm{c}) \times 11=(\mathrm{b}+\mathrm{c}) \times 5$
$\Rightarrow 11 \mathrm{b}-11 \mathrm{c}=5 \mathrm{b}+5 \mathrm{c}$
$\Rightarrow 6 \mathrm{b}=16 \mathrm{c}$
$\Rightarrow \frac{b}{c}=\frac{16}{6}=\frac{8}{3}=8: 3$
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