Multiple choice

The speed of a stream is 3 km/hr. and the speed of a man in still water is 5 km/hr. The time taken by the man to swim 52 km downstream is

  1. $8(2/3) hrs.$
  2. $6(1/2) hrs.$
  3. $13 hrs.$
  4. $5(1/5) hrs.$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Downstream speed = Man's speed in still water + Stream speed = 5 + 3 = 8 km/hr. Time = Distance/Speed = 52/8 = 6.5 hours = 6(1/2) hours. When swimming downstream, the stream assists the swimmer, so effective speed is additive.

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