Instructions: Each of the following questions consists of a question followed by three statements I, II and III. You have to study the question and the statements and decide which of the statement (s) is/are necessary to answer the question.
What is the speed of boat in still water?
I. The boat covers 12 km in 2 hours in downstream.
II. The boat covers same distance in 4 hours in upstream.
III. The speed of stream is one third of that of boat in still water.
Downstream = boat + stream = $$\frac{12}{2}$$ + stream = 6 km/hr
Upstream =boat - stream = $$\frac{12}{4}$$ - stream = 3 km/hr
Solving the above equations we get boat = 4.5 km/hr and stream = 6 - 4.5 = 1.5
Speed of the stream = $$\frac{1}{3}$$rd of that of the boat in still river = 1.5
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