Question

the length and breadth of
a rectangle increase by 20%
What would be change
in area of rectangle.
​

Answer 1

l'=l+20/100l

l'=1.2 l

similarly b'=1.2 b

orignal area= lb = x(say)

new area=l' b'

= 1.44 lb

= 1.44 x

so change = new- orignal

=1.44 - 1

= 0.44 orignal area

Answer 2

Let us take the length and breadth of the rectangle be l and b respectively.

Then the area of the rectangle =(lenght×breadth) =(l×b)=lb.

Length of rectangle increased by 20% = 120/100×l = 6/5l.

Breadth of the rectangle increased by 20% = 120/100×b=6/5b.

Therefore area of rectangle = ( length+breadth) =(1/5l ×1/5b) = 36lb/25.

Therefore change in area =36lb/25 - lb =900lb - lb /25 = 899lb/25.