Miscellaneous Question 18
- A boat travels from A to B upstream and then from B to C downstream taking the same time. The respective ratio between the distance from $A$ to $B$ and the distance from $B$ to $C$ is 5 : 7. If the boat takes 2 hours 30 minutes to travel a distance of $35 $ $km$ downstream, what is the speed of the stream? (in $km / h$ )
(1) $2$ $ kmph$
(2) $1.5$ $ kmph$
(3) $2.5$ $ kmph$
(4) $2.2$ $ kmph$
(5) None of these
(SIDBI Officer Online Exam.24.02.2016)
Show Answer
Correct Answer: 18. (1)
Solution: 18. (1) $\mathrm{AB}=5 x \mathrm{km}$.
$\mathrm{BC}=7 x$ $ \mathrm{km}$.
Rate downstream of boat
$=\frac{35}{2 \frac{1}{2}}=\frac{35 \times 2}{5}=14 $ $ \mathrm{kmph}$
Rate upstream of boat
$=y$ $ \mathrm{kmph}$
According to the question,
$\frac{5 x}{y}=\frac{7 x}{14}$
$\Rightarrow \frac{5}{y}=\frac{1}{2} \Rightarrow y=10$ $ \mathrm{kmph}$
$\therefore$ Speed of current
$=\frac{1}{2}(14-10) \mathrm{kmph}$
$=2 $ $\mathrm{kmph}$
BETA
