Multiple choice

Twice the speed of a boat downstream is equal to thrice the speed upstream. The ratio of its speed in still water to its speed in current is

  1. $1 : 5$
  2. $1 : 3$
  3. $5 : 1$
  4. $2 : 3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let b be boat speed and c be current speed. Downstream speed is b+c, upstream is b-c. Given 2(b+c) = 3(b-c), so 2b + 2c = 3b - 3c, which simplifies to b = 5c. The ratio b:c is 5:1.

AI explanation

Using the formulas for downstream and upstream speeds, we write the equation 2 multiplied by the sum of the boat speed and stream speed equals 3 multiplied by the difference of the boat speed and stream speed. Expanding both sides gives 2b + 2s = 3b - 3s, and rearranging terms yields b = 5s. Therefore, the ratio of the speed of the boat in still water to the speed in the current is 5 to 1.

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