Multiple choice

Ratio of upstream speed to downstream speed is 1:11. If speed of boat is 30 km/hr. Find the distance covered in upstream in 5 hours? (in km)

  1. 66

  2. 55

  3. 25

  4. 30

  5. 40
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let upstream speed be u and downstream speed be d. Given u/d = 1/11, so d = 11u. Boat speed = (u + d)/2 = 6u = 30, so u = 5 km/hr. Distance = speed * time = 5 * 5 = 25 km.

AI explanation

Using the formula for boat speed where speed of boat equals 0.5 times the sum of upstream and downstream speeds, we find the speed difference between the boat and the upstream speed is proportional. Given the ratio of upstream to downstream speed as 1:11, the difference between downstream and upstream speeds is 10 units. The speed of the boat is the average of these speeds, which is 6 units. Setting 6 units equal to 30 km/hr makes 1 unit equal to 5 km/hr. Therefore, the upstream speed is 5 km/hr, and multiplying by 5 hours gives the distance as 25 km.

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