Q. 18

The length of a rectangle is increased by 15% and the breadth is reduced by 15%. Let’s work out in percentage the increase or decrease of area.

Answer :

Given: The percentage increment of the length of the rectangle=15%


The percentage decrement of the breadth of the rectangle=15%


Tip: if y is increased by x% then the new value of y is



: if y is decreased by x%, then the new value of y is



Let the length of the rectangle be “L” units.


Let the breadth of the rectangle be B units


Therefore, initially before any change in the lengths of both the length and breadth of the rectangle is


=


Now, Using tip (i)


The new length of the rectangle will be:


=L units =L units


Now, Using tip (ii)


The new breadth of the rectangle will be:


=B units. =B units


Therefore, the new area of the rectangle will be:


=LB


=LB


Therefore, the decrement in area= LB- LB


=LB


Therefore, percentage decrement in area,


=


=


=2.25%


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