A motorboat in still water travels at speed of 36 kmph. It goes 56 km upstream in 1 hour 45 minutes. The time taken by it to cover the same distance down the stream will be:
A. 2 Hours 25 Minutes B. 3 Hours C. 1 Hours 24 Minutes D. 2 Hours 21 Minutes Answer: Option CShow Answer
Solution(By Apex Team)
1 hour 45 minutes $=1+\frac{45}{60}=\frac{7}{4} \text { hours }$
$\begin{array}{l}
=\frac{\text { Distance }}{\text { Time Taker }} \\
=\frac{56 \mathrm{~km}}{\frac{7}{4} \text { hours }} \\
=\frac{56 \times 4}{7} \\
=32 \mathrm{kmph}
\end{array}$
Let the speed of the current = x kmph
Hence, 36 – x = 32
Or, x = 36 – 32 = 4 kmph
Speed of boat down the stream = 36 + 4 = 40 kmph.
∴ Time taken to cover 56 km at 40 kmph $=\frac{56}{40}=\frac{7}{5} \text { hours }$
or 1 hours 24 minutes.
