Question

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

    his speed by 10 km/h after every hour. He reached his destination in 20 hours. If his initial speed was 25 km/h, then what was his average speed in the whole journey?
    A 100 km/h Correct Answer Incorrect Answer
    B 140 km/h Correct Answer Incorrect Answer
    C 80 km/h Correct Answer Incorrect Answer
    D 120 km/h Correct Answer Incorrect Answer

    Solution

    Total distance travelled by A = (20/2) × {2 × 25 + (20 – 1) × 10} = 10 × (50 + 190) = 2400 km Required average speed = 2400/20 = 120 km/h

    Practice Next