Multiple choice

A boat takes 3 hours to travel 30 km downstream and takes 5 hours to return to the same spot upstream. Find the speed of the boat in still water. (km/hr)

  1. 10 km/hr

  2. 8 km/hr

  3. 6 km/hr

  4. 5 km/hr
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B Correct answer
Explanation

Downstream speed (v+u) = 30/3 = 10 km/hr. Upstream speed (v-u) = 30/5 = 6 km/hr. Still water speed v = (10+6)/2 = 8 km/hr.

AI explanation

Using the formula for speed, the downstream speed is 30 km divided by 3 hours, which equals 10 km/hr. The upstream speed is 30 km divided by 5 hours, which equals 6 km/hr. The speed of the boat in still water is half the sum of the downstream and upstream speeds, giving (10 + 6) / 2 = 8 km/hr. The result is 8 km/hr.

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