Question

Radius of a circle is 10 cm if its diameter is increased by 100% its area is increased by
a) 150%
b) 200%
c) 250%
d) 300%​

Answer 1

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d) 300%

Explanation

Let the radius of circle is r

Then area of circle= πr^2

If radius increased 100%

then new radius= r × 200/ 100

=2r

Then area of new circle= π(2r) ^2

=4πr^2

Then increased in area =4πr^2 − πr^2

=3πr^2

So % of increased in area

= 3πr^2 / πr^2 ×100

= 300%

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