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    Question

    A boat takes 30 hours to move 300 km upstream. If the

    boat doubles its speed, then it covers 300 km downstream in 6 hours. Find the speed of the stream.
    A 10 km/h Correct Answer Incorrect Answer
    B 20 km/h Correct Answer Incorrect Answer
    C 30 km/h Correct Answer Incorrect Answer
    D 45 km/h Correct Answer Incorrect Answer

    Solution

    Upstream speed = 300 ÷ 30 = 10 km/h Let boat’s speed in still water = 'x' and stream speed = 'y'. So, x - y = 10 ...... (I) Downstream speed when doubled = 300 ÷ 6 = 50 So, 2x + y = 50 ......... (II) Adding (I) and (II): 3x = 60 x = 20 So, 20 - y = 10 y = 10 Stream speed = 10 km/h

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