Passage

Directions: The following question is accompanied by statements (A), (B) and (C). You have to determine which of the following statements is/are sufficient/necessary to answer the question.

What is the speed of boat in still water and the speed of stream? (A) The speed of the stream is one-fifth that of the boat in still water. (B) The boat covers 24 km in 3 hours upstream. (C) The boat covers 48 km in 4 hours downstream.

Using B, the upstream speed is 24/3 = 8 km/h, so 8 = x - y. Combined with A, y = x/5, so 8 = x - x/5 = 4x/5, which gives x = 10 km/h and y = 2 km/h. The same applies using C, where the downstream speed is 48/4 = 12 km/h, so 12 = x + y, and combining with A gives x = 10 km/h and y = 2 km/h. A and either B or C are sufficient.

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• Wrong explanation