Question

    A policeman noticed a thief at a distance of 500 metres.

    The policeman started running and the thief also started running at the same time. The thief is running at a speed of 15 km/h. It took 15 minutes for the policeman to catch the thief. Find the speed of the policeman (in km/h). 
    A 11 Correct Answer Incorrect Answer
    B 17 Correct Answer Incorrect Answer
    C 12 Correct Answer Incorrect Answer
    D 10 Correct Answer Incorrect Answer

    Solution

    Let the speed of the policeman be x km/h. The thief runs at 15 km/h and was 500 meters (0.5 km) ahead. Time taken to catch the thief is 15 minutes = 0.25 hours. Relative speed = x − 15 km/h Distance = 0.5 km Time = 0.25 hours Using the formula: Distance = Speed ×Time 0.5 =(x − 15) × 0.25 0.5/0.25 = x − 15 2 = x − 15 x = 17

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