Length and breadth of a rectangle are increased by 10% and 20% respectively. What will be the percentage increase in the area of rectangle?

Let both length and breadth of the rectangle be $$l=10$$ cm and $$b=10$$ cm

Area of rectangle = $$A=l\times b=10\times10=100$$ $$cm^2$$

New length when it is increased by 10% = $$l'=10+(\frac{10}{100}\times10)=11$$ cm

Similarly, new breadth when it is increased by 20% = $$b'=10+(\frac{20}{100}\times10)=12$$ cm

=> New area = $$A'=11\times12=132$$ $$cm^2$$

$$\therefore$$ % increase = $$\frac{(132-100)}{100}\times100=32\%$$

=> Ans - (B)