On decreasing the radius of a circle by 30%, its area is decreased by

Let the radius if circle be r


Area of circle = A = πr2


Radius decreases by 30%


So, New Radius r’ = r - 30/100 × r = 0.7r


New Area of circle = A’ = πr’2 = π × (0.7r)2


= .49πr2


Percentage decrease in area =


= = .51 × 100 = 51


Decrease in area = 51%

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