Jharkhand PSC Prelim Exam 2006 Solved Paper

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Question : 82 of 100

Marks: +1, -0

The radius of a circle is to be increase 100%, if the area will increase.

100%
200%
300%
400%

Solution:

Area of circle

=π r^{2}

if radius of a circle is increased by

100 \%,

then the radius

= {r}+ {r} × \;{100}/{100} × 2 {r}

∴

New area

=π(2 r)^{2}

=π × 4 r^{2}=4 π r^{2}

∴

Difference between areas

=4 π r^{2}-π r^{2}

=3 π r^{2}

Increase in

\%

of Area

=\;{3 π r^{2} × 100}/{π r^{2}}=300 \%

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