Question

the lenght of a rectangle increases by 20% and the breadth decrease by 10%,by what%will the area change

Answer 1

let the length be x
and breadth be y.
then area = xy
ACCORDING TO QUESTION.
increase of 20% in length.
$length \: of \: rectangle \: = \frac{120x}{100}$
Decrease of 10% in breadth.
$breadth \: of \: rectangle \: = \frac{90y}{100}$
then new area of rectangle.
$\frac{120x}{100} \times \frac{90y}{100} = \frac{10800xy}{10000} \:= \frac{108xy}{100}$
now comparing new area with previous area.
$xy \times n = \frac{108xy}{100} \\ n = 108 \\ 108 - 100 = 8 \\it \: means \: 8\%.$
Area of rectangle will change by 8%.
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