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A boat can travel 4.2 km upstream in 14 minutes. If the respective ratio of speed of the boat in still water and speed of the stream is 7 : 1. How much time will the boat take to cover 17.6 km downstream ? (in minutes)

A) 52
B) 44
C) 48
D) 36

Correct Answer:


B) 44

Description for Correct answer:
Speed of current = x kmph

\( \Large \therefore \) Speed of the boat in still water = 7x kmph

\( \Large \therefore \) Rate upstream

7x - x = 6x kmph

\( \Large \therefore \frac{Distance}{speed} = time \)

=> \( \Large \frac{4.2}{6x} = \frac{14}{60} \)

=> \( \Large 14x = 42 => x = \frac{42}{14} = 3 \)

Rate downstream

= 7x + x = 8x

\( \Large 8 \times 3 = 24 \ kmph \)

Time taken in covering 17.6 km

= \( \Large \frac{17.6}{24} \ hour \)

= \( \Large (\frac{17.6 \times 60}{24} ) \ minutes \)

= 44 minutes

Part of solved Aptitude questions and answers : >> Aptitude

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