Multiple choice

A boat can cover 80km downstream in double time in which 80km upstream can be covered. If in 3 hours boat can cover 48km downstream then find the speed of stream?

  1. 3 km/hr

  2. 4 km/hr

  3. 1.5 km/hr

  4. 2 km/hr

  5. 2.5 km/hr
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let v be boat speed and s be stream speed. Downstream speed = v+s, upstream = v-s. 80/(v-s) = 2 * 80/(v+s) => v+s = 2v-2s => v = 3s. 48/(v+s) = 3 => v+s = 16. 3s+s = 16 => 4s = 16 => s = 4.

AI explanation

The downstream speed is calculated as 48 km divided by 3 hours, which equals 16 km/hr. Since the boat takes double the time to cover the same distance upstream, the upstream speed is half of the downstream speed, making it 8 km/hr. Using the formula where the speed of the stream equals 0.5 times the difference of downstream and upstream speeds, we compute 0.5 times (16 minus 8). This calculation gives the speed of the stream as 4 km/hr.

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