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    Question

    Suresh started his journey form P to Q by his bike at

    the speed of 40 km/h and then, the same distance he travelled on his foot at the speed of 10 km/h from Q to R. Then he returned from R to P via Q at the speed of 24 km/h. The average speed of the whole trip is:
    A 18.5 km/h Correct Answer Incorrect Answer
    B 19.8 km/h Correct Answer Incorrect Answer
    C 18.2 km/h Correct Answer Incorrect Answer
    D 19.2 km/h Correct Answer Incorrect Answer

    Solution

    ATQ, we can say that Let the distance between P and Q be 120 km. (LCM of 40, 10 and 24 = 120) PQ = QR = 120 km RP = 2 × 120 = 240 km Time taken by Suresh from point P to Q = Distance/Speed = 120/40 = 3 hours Time taken by Suresh from point Q to R = Distance/Speed = 120/10 = 12 hours Time taken by Suresh from point R to P = Distance/Speed = 240/24 = 10 hours ∴ Average Speed = (120 + 120 + 240) / (3 + 12 + 10) = 480/25 = 19.2 km/hr

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