If the base of triangle is increased by 10% and height is decreased by 20%, then what will be the percentage change in the area of a triangle?

Let the base and height of the triangle be $$10$$ cm

Area of triangle = $$\frac{1}{2}\times10\times10=50$$ $$cm^2$$

After increasing the base by 10%, => New base = $$10+(\frac{10}{100}\times10)$$

= $$10+1=11$$ cm

Similarly, new height = $$10-(\frac{20}{100}\times10)$$

= $$10-2=8$$ cm

=> New area = $$\frac{1}{2}\times11\times8=44$$ $$cm^2$$

$$\therefore$$ Decrease in area = $$\frac{(50-44)}{50}\times100=12\%$$

=> Ans - (D)