If the radius of a circle is increased by 20% then by how much will its area be increased? · ABC26GN4293

Let original radius $=R$. New radius $=\frac{120}{100} R=\frac{6 R}{5}$. Original area $=\pi R^{2}$ and New area $=\pi\left(\frac{6 R}{5}\right)^{2}=\frac{36 \pi R^{2}}{25}$. Increase in area $=\left(\frac{36 \pi R^{2}}{25}-\pi R^{2}\right)=\frac{11 \pi R^{2}}{25}$. ∴ Increase $\%=\left(\frac{11 \pi R^{2}}{25} \times \frac{1}{\pi R^{2}} \times 100\right) \%=44 \%$.