Book: RS Aggarwal - Mathematics
Chapter: 18. Area of Circle, Sector and Segment
Subject: Maths - Class 10th
Q. No. 6 of Multiple Choice Questions (MCQ)
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6
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%
