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    Question

    A boat covers a distance of 45 km in still water in 2.5

    hours. The ratio of its speed while traveling upstream to its speed while traveling downstream is 4:5. What is the speed of the stream?
    A 5 km/hr Correct Answer Incorrect Answer
    B 3 km/hr Correct Answer Incorrect Answer
    C 2 km/hr Correct Answer Incorrect Answer
    D 4 km/hr Correct Answer Incorrect Answer

    Solution

    Speed of the boat in still water = 45 ÷ 2.5 = 18 km/hLet the speed of the stream = 'x' km/hUpstream speed of the boat = (18 - x) km/hDownstream speed of the boat = (18 + x) km/hAccording to the question,(18 - x):(18 + x) = 4:5Or 90 - 5x = 72 + 4xOr, 18 = 9xSo, x = (18/9) = 2

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