Multiple choice

A boat can go $72 km$ downstream in $4$ hours and $36 km$ upstream in $3$ hours. Calculate the speed of stream.

  1. $7 km/hr$
  2. $3 km/hr$
  3. $12 km/hr$
  4. $6 km/hr$
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B Correct answer
Explanation

Downstream speed = 72/4 = 18 km/hr. Upstream speed = 36/3 = 12 km/hr. Speed of stream = (Downstream - Upstream)/2 = (18 - 12)/2 = 3 km/hr.

AI explanation

Using the formula for speed, the downstream speed is 72 km / 4 hr = 18 km/hr and the upstream speed is 36 km / 3 hr = 12 km/hr. The speed of the stream is half the difference of the downstream and upstream speeds, which gives (18 - 12) / 2 = 3 km/hr. The result is 3 km/hr.

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