On decreasing the radius of a circle by 30%, its area is decreased byA. 30%B. 60%C. 45%D. none of these

Let the radius if circle be r

Area of circle = A = πr2

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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