Multiple choice

What is the speed of the boat in still water? I. The boat covers a distance of 48 kms in 6 hours while running upstream. II. The boat covers the same distance in 4 hours while running downstream.

  1. I alone sufficient while II alone not sufficient to answer

  2. II alone sufficient while I alone not sufficient to answer

  3. Either I or II alone sufficient to answer

  4. Both I and II are not sufficient to answer

  5. Both I and II are necessary to answer
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Let boat speed be b and current speed be c. Upstream: b - c = 48/6 = 8. Downstream: b + c = 48/4 = 12. Adding the equations gives 2b = 20, so b = 10. Both statements are required to find both variables.

AI explanation

Let the speed of the boat in still water be B and the speed of the stream be S. From statement I, the upstream speed (B - S) equals 48 km / 6 hours, which is 8 kmph. From statement II, the downstream speed (B + S) equals 48 km / 4 hours, which is 12 kmph. Solving these two equations by adding them gives 2B = 20, so B = 10 kmph; therefore, both statements are necessary.

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