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  1. If the radius of a circle is decreased by 10%, then the area of the circle is decreased by
    1. 89%
    2. 18%
    3. 19%
    4. 25%
Correct Option: C

Using Rule 12,

Percentage decrease = 2x +
x²
 %
100

= 2 × ( - 10) +
(-10)²
 %
100

= (– 20 + 1)% = – 19%


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