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    Question

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

    his speed by 14 km/h after every hour. He reached his destination in 18 hours. If his initial speed was 20 km/h, then what was his average speed in the whole journey?
    A 129 km/h Correct Answer Incorrect Answer
    B 119 km/h Correct Answer Incorrect Answer
    C 109 km/h Correct Answer Incorrect Answer
    D 139 km/h Correct Answer Incorrect Answer

    Solution

    Total distance travelled by A = (18/2) × {2 × 20 + (18 – 1) × 14} = 14 × (40 + 238) = 2502 km Required average speed = 2502/18 = 139 km/h

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