Question

    A is cycling at an average speed of 10 km/hr such that

    he can reach a certain point at 12 noon. If he cycles at 15 km/hr, then he will reach the destination at 10 a.m. At what speed he should cycle to reach the destination at 11 a.m.
    A 12 km/hr Correct Answer Incorrect Answer
    B 10 km/hr Correct Answer Incorrect Answer
    C 11 km/hr Correct Answer Incorrect Answer
    D 15 km/hr Correct Answer Incorrect Answer

    Solution

    Let the distance to be travelled be ‘x’ km Time taken when speed is 10 km/hr = (x/10) hours Time taken when speed is 15 km/hr = (x/15) hours According to the question, (x/10) – (x/15) = 2 Or, 3x – 2x = 2 × 30 Or, x = 60 km Time taken to travel 60 km with speed of 10 km/hr = 60/10 = 6 hours Therefore, he started at 12 – 6 = 6 a.m. Therefore, required speed to reach the destination at 11 a.m. or 5 hours = 60/5 = 12 km/hr

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