Multiple choice

A motorboat takes $2$ hours to travel a distance of $9$ km down the current and it takes $6$ hours to travel the same distance against the current. What is the speed of the boat in still water in kmph?

  1. $3$
  2. $2$
  3. $1.5$
  4. $1$
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A Correct answer
Explanation

Let boat speed be B and current speed be C. Downstream: B+C = 9/2 = 4.5. Upstream: B-C = 9/6 = 1.5. Adding equations: 2B = 6, so B = 3.

AI explanation

The downstream speed is calculated as Distance / Time, which gives 9 km / 2 hours = 4.5 kmph. The upstream speed is similarly 9 km / 6 hours = 1.5 kmph. Using the formula for a boat's speed in still water, Speed = (Downstream Speed + Upstream Speed) / 2, we get (4.5 + 1.5) / 2 = 3 kmph. The result is 3.

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