SSC GD Constable 2015 · Question 28 of 88

If the radius of a circle is decreased by 10% then the area of the circle is decreased by

percentage

A89%
B18%
C19%Correct
D25%

Answer: C. 19%

Explanation

Let radius of circle = r = 10 cm => Area of circle = A = πr2 = π(10)2 = 100π cm2 10 After decreasing the radius by 10%, => New radius = r′ = 10 − ( 100 × 10) = 9 cm => New area of circle = A′ = π(9)2 = 81π cm2 ∴ Decrease in area = (100−81) 100 × 100 = 19% => Ans - (C)

Source: Solved SSC GD 2015 Paper with Solutions — Collegedunia · reliable-secondary

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