New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    The area of a circle got increased by 22 cm² when the

    radius was increased by 1 cm. d by 1 cm. What was the original radius?
    A 9 cm Correct Answer Incorrect Answer
    B 5 cm Correct Answer Incorrect Answer
    C 7 cm Correct Answer Incorrect Answer
    D 3 cm Correct Answer Incorrect Answer

    Solution

    Let the radius of the circle be r cm new radius of the circle = (r + 1) As we know, Area of the circle = πr² According to the question - π (r + 1) ² – πr² = 22 π [ r+ 1)2-r2] = 22   (22/7) [r² + 1 + 2r - r² ] = 22   (1 + 2r) = 7 2r = 7-1 r = 6/2 r = 3 cm.

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