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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 C
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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.

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