Question

    A boatman rows 10 km in 15 minutes, along the stream and

    50 km in 2 hours against the stream. The speed of the stream is:
    A 26 km/hr Correct Answer Incorrect Answer
    B 15 km/hr Correct Answer Incorrect Answer
    C 30 km/hr Correct Answer Incorrect Answer
    D 7.5 km/hr Correct Answer Incorrect Answer
    E 22.5 km/hr Correct Answer Incorrect Answer

    Solution

    Rate downstream = 10/15 x 60 = 40 km/hr Rate upstream = 50/2 = 25 km/hr Speed of current = 1/2 (Rate downstream – Rate upstream) ⇒ 1/2 (40 – 25) km/hr = 7.5 km/hr

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