Question

What is the area of a rectangle if perimeter is 21 cm

Answer 1

perimeter=2(l+b)
21=2(x+2x)
21/2=x+2x
21/2*3=x
3.5=x
area=7*3.5
=24.5

Answer 2

The area of a rectangle is 24.5 $cm^{2}$  if the perimeter is 21 cm

Given,

Perimeter = 21cm

To find,

The area of a rectangle

Solution,

The perimeter of a rectangle:

• The Perimeter of a rectangle is the length of the outline of a shape.

• It could be considered as one of the important formulae of the rectangle.  As It is the total distance covered by the rectangle around its outside.

• There are four sides of a rectangle, thus, the perimeter of the rectangle will be the sum of all four sides.

• The unit of the perimeter of the rectangle will be in meters, centimeters, inches, feet, etc.

• From the definition of the perimeter we know, the perimeter of a rectangle, P = 2 ( x+y) units

where

“x” is the length of the rectangle

“y” is the breadth of the rectangle

Let us consider, x = 2a, y = a

from the perimeter formula,

P = 2 ( x+y )

P = 2 (2a + a)

P = 2 (3a)

As the given perimeter is 21cm,

21 = 2 (3a)

a = 7/2

a = 3.5cm, which is the value of y.

So, x = 2 * 3.5

x = 7

Area of rectangle = length * breadth

Area of rectangle = 7 * 3.5

The area of a rectangle is 24.5 $cm^{2}$

The area of a rectangle is 24.5 $cm^{2}$  if the perimeter is 21 cm

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