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    Question

    A circular lawn has an inner radius of 21 metres. A

    track of width 7 metres surrounds the lawn. Find the cost of colouring the track at the rate of Rs. 8 per square metre.
    A Rs. 8624 Correct Answer Incorrect Answer
    B Rs. 8000 Correct Answer Incorrect Answer
    C Rs. 8360 Correct Answer Incorrect Answer
    D Rs. 7200 Correct Answer Incorrect Answer

    Solution

    Outer radius = 21 + 7 = 28 metres Area of outer circle = π × 28²
    = (22/7) × 784
    = 2464 m² Area of inner circle = π × 21²
    = (22/7) × 441
    = 1386 m² Area of the track = 2464 − 1386
    = 1078 m² Therefore, cost of colouring the track = 1078 × 8
    = Rs. 8624

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