A man can swim $3 k m / h r$ in still water. If the velocity of the stream is $2 k m / h r$ , the
time taken by him to swim to a place $10 k m$ upstream and back is :

9 \frac{1}{3} h r

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10 h r

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12 h r

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8 \frac{1}{3} h r

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Solution

The correct option is C $12 h r$
Velocity of man upstream $V_{u}$ = Velocity of man - Velocity of stream = $3 k m / h r - 2 k m / h r = 1 k m / h r$
Time taken to travel upstream = $t_{u} = d / V_{u} = \frac{10 k m}{1 k m / h r} = 1 h r$
Velocity of man downstream $V_{d}$ =Velocity of man+Velocity of stream= $3 k m / h r + 2 k m / h r = 5 k m / h r$
Time taken to travel downstream = $t_{d} = d / V_{d} = \frac{10 k m}{5 k m / h r} = 2 h r$
Total time = $t_{u} + t_{d} = 10 h r + 2 h r = 12 h r$

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A man can swim 3 km/hr in still water. If the velocity of the stream is 2 km/hr, thetime taken by him to swim to a place 10 km upstream and back is :

A man can swim $3 k m / h r$ in still water. If the velocity of the stream is $2 k m / h r$ , the
time taken by him to swim to a place $10 k m$ upstream and back is :