Question

    A journey of 420 km is completed partly on foot and partly

    by bicycle. Walking speed is 6 km/h and biking speed is 21 km/h. If 25% of the distance is walked, what is the average speed of the journey (nearest whole number)?
    A 13 km/h Correct Answer Incorrect Answer
    B 31 km/h Correct Answer Incorrect Answer
    C 28 km/h Correct Answer Incorrect Answer
    D 45 km/h Correct Answer Incorrect Answer

    Solution

    ATQ,

    Time taken on foot = [(0.25 × 420)/6] = (105/6) = 17.5 hours

    Time taken by bicycle = [(0.75 × 420)/21] = (315/21) = 15 hours

    Average speed = [(Total distance)/(Total time)] = [420/(17.5 + 15)] = (420/32.5) ~ 13 km/h

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