ABC26GN4269 · Area

Let the base and height of the triangle be $x$ and $y$ units respectively. Then, area of the triangle $=\left(\frac{1}{2} x y\right)$ sq. units. $$\begin{aligned} & \text { New, area }=\left[\frac{1}{2}(80 \% \text { of } x)(130 \% \text { of } y)\right] \text { sq. units. } \\ & \qquad=\left(\frac{1}{2} \times \frac{4 x}{5} \times \frac{13 y}{10}\right) \text { sq.units }=\left(\frac{13 x y}{25}\right) \text { sq.units. } \\ & \text { Increase in area }=\left(\frac{13 x y}{25}-\frac{x y}{2}\right) \text { sq.units }=\left(\frac{x y}{50}\right) \text { sq.units. } \\ & \therefore \text { Increase } \%=\left(\frac{x y}{50} \times \frac{2}{x y} \times 100\right) \%=4 \% . \end{aligned}$$