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    Question

    A driver covers a distance in three stages. In the first

    'z - 50' km, he drives at 40 km/h, for the next 'z' km at 60 km/h, and the remaining 'z + 50' km at 50 km/h. If the overall average speed is 50 km/h, calculate 'z'.
    A 150 Correct Answer Incorrect Answer
    B 210 Correct Answer Incorrect Answer
    C 125 Correct Answer Incorrect Answer
    D 165 Correct Answer Incorrect Answer
    E none of these Correct Answer Incorrect Answer

    Solution

    ATQ, Let the total distance covered is: (z−50)+z+(z+50)=3z The total time taken is the sum of the time for each segment: Then, Average Speed Equation: Average Speed= (Total Distance/Total Time) = 50 km/h Now, Set Up the Equation: Then, solve for 'z' Find a common denominator (600) and combine terms: Cross-multiply and solve: 1800z = 1850z - 7500 7500 − 50z = -7500  z = 150

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