Multiple choice

What is the speed of the boat in stagnant water? (I) Boat goes downstream 15 km in 2 hours. (II) Ratio of speed of boat to water current is 10:3

  1. If statement I alone is sufficient, but statement II alone is not sufficient

  2. Statement II alone is sufficient, but statement I alone is not sufficient

  3. If both statements I and II together are sufficient, but neither statement alone is sufficient

  4. If statements I and II together are not sufficient
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Statement I: downstream distance = 15 km in 2 hours, so downstream speed = 7.5 km/h = boat speed + current speed. Statement II: boat speed : current speed = 10 : 3. Neither alone gives the answer, but together: let boat speed = 10x, current = 3x. Then 10x + 3x = 7.5, so 13x = 7.5, x = 7.5/13. Boat speed = 10x = 75/13 km/h. Both together are sufficient, but neither alone - answer is C.

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