Question

If Perimeter of a rectangle increases by $30$% , what will be the effect on its area ?

Answer 1

Let the length and breadth be $l$ and $b$ then

Perimeter $=2(l+b)$

Given that the perimeter is increased by $30\%$, it means that the length and the breadth both are increased by $30\%$

$\delta l=30\%$, $\delta b=30\%$

Let the area increase by $x$ then

$x=\delta l+\delta b+\frac{\delta l\times \delta b}{100}$

$x=30+30+\frac{30\times 30}{100}$

$x=69\%.$

This is the required solution.