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A person can row a boat d km upstream and the same distance downstream in \( \Large 5 \frac{1}{4} \ hours \). Also he can row the boat 2d km upstream in 7 hours. He will row the same distance downstream in

A) \( \Large 3 \frac{1}{2} \ hours \)
B) \( \Large 3 \frac{1}{4} \ hours \)
C) \( \Large 4 \frac{1}{4} \ hours \)
D) 4 hours

Correct Answer:

A) \( \Large 3 \frac{1}{2} \ hours \)

Description for Correct answer:
Let the speed of boat in still water he x kmph and that of current by y kmph.

According to the question,

\( \Large \therefore \frac{d}{x + y} + \frac{d}{x - y} = \frac{21}{4} \) ... (i)

and, \( \Large \frac{2d}{x - y} = 7 => \frac{d}{x - y} = \frac{7}{2} \) ...(ii)

By equation (ii) - (i),

\( \Large \frac{d}{x + y} = \frac{21}{4} - \frac{7}{2} = \frac{21 - 14}{4} = \frac{7}{4} \)

=> \( \Large \frac{2d}{x + y} = \frac{7}{2} = 3 \frac{1}{2} hours \)

Part of solved Aptitude questions and answers : >> Aptitude

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