Question

    A was travelling from point X to point Y. He increased

    his speed by 8 km/h after every hour. He reached his destination in 12 hours. If his initial speed was 20 km/h, then what was his average speed in the whole journey?
    A 60 km/h Correct Answer Incorrect Answer
    B 61 km/h Correct Answer Incorrect Answer
    C 63 km/h Correct Answer Incorrect Answer
    D 64 km/h Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Total distance travelled by A = (12/2) × {2 × 20 + (12 – 1) × 8} = 5 × (40 + 88) = 768 km Required average speed = 768/12 = 64 km/h

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