Question

The length and breadth of a rectangle are increased by 20% and 40% respectively. what is the percentage increase in its area?

Answer 1

Let the Original length=l
original breadth=b
original area= l ×b

New area:
new length=(120/100)×l =
6l/5

new breadth=(140/100)×b
=7b/5
area= (6l/5)(7b/5)
=42lb/25

% increase = (new area- original area)×100/original area

=(((42lb/25)-lb)×100)/lb
(((42lb - 25lb) /25 ) ×100)/lb

((17lb/25)×100))/lb

=68 %

The percentage increase in its area is 68%

Answer 2

Answer:

Let the original length = l

original breadth = b

original area = l×b

new area :

new length =(120/100)×l=61/5

new breadth=(140/100)×b

=7b/5

area = (61/5)(7b/5)

=421b/25

% increase =(new area- original area)×100/ original area

=(((421b/25)-lb)×100)/lb

(((421b - 25lb) / 25) × 100)/lb

(((17lb/25)×100))/lb

=68%

The percentage increase in its area is 68%