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    Question

    A car moves from city ‘A’ to city ‘B’ at 50 km/h

    and returns back from city ‘B’ to city ‘A’ at 75 km/h. Find the car’s average speed during the entire round trip.
    A 52 km/h Correct Answer Incorrect Answer
    B 60 km/h Correct Answer Incorrect Answer
    C 75 km/h Correct Answer Incorrect Answer
    D 40 km/h Correct Answer Incorrect Answer

    Solution

    ATQ,


    Let the distance between city ‘A’ and ‘B’ = D km

    Average speed = Total distance / Total time

    Average speed = (D + D) / [(D / 50) + (D / 75)]

    = 2D / [(3D + 2D)/150]

    = 2D / (5D / 150)

    = (2D / 5D) × 150

    = 60 km/h

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