Multiple choice

A man rows downstream $30$ km and upstream $18$ km, taking $5$ hours each time. The velocity of current is ____________.

  1. $1.2$ km/hr
  2. $6$ km/hr
  3. $3.6$ km/hr
  4. $2.4$ km/hr
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A Correct answer
Explanation

Downstream speed = 30/5 = 6 km/hr. Upstream speed = 18/5 = 3.6 km/hr. Current velocity = (Downstream - Upstream) / 2 = (6 - 3.6) / 2 = 2.4 / 2 = 1.2 km/hr.

AI explanation

The speed downstream is calculated as distance divided by time, which is 30 km divided by 5 hours to equal 6 km/hr. The speed upstream is 18 km divided by 5 hours, which equals 3.6 km/hr. The velocity of the current is found by the formula half of the difference between downstream and upstream speeds. This gives (6 - 3.6) divided by 2, resulting in a current velocity of 1.2 km/hr.

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