If each side of a square is increased by 10%, its area will be increased by · ABC26GN4417

Let original length of side be $x$. Then, new length $=(110 \%$ of $x)=\frac{11 x}{10}$. Original area $=x^{2}$ New area $=\left(\frac{11 x}{10}\right)^{2}=\frac{121 x^{2}}{100}$. Increase in area $=\left(\frac{121 x^{2}}{100}-x^{2}\right)=\frac{21 x^{2}}{100}$. ∴ $\quad$ Increase $\%=\left(\frac{21 x^{2}}{100} \times \frac{1}{x^{2}} \times 100\right) \%=21 \%$.