AreaCalculate the area of a rectangle whose perimeter is 40 and the length is 4 more than 4 time the width.

giorgiana1976 | Student

To calculate the area of the rectangle, we'll have to know the values of the lengths of the sides of the rectangle.

Let's note the length as a and the width as b.

From enunciation we know that:

a = 4 + 4b (1)

From enunciation we also know that the perimeter is 40 units.

The formula for perimeter of a rectangle is:

P = 2(a+b)

40 = 2(a+b)

We'll divide by 2 and we'll use the symmetric property:

a+b = 20 (2)

To calculate a and b we have to solve the system of equations (1) and (2).

We'll substitute (1) in (2):

4 + 4b + b = 20

We'll subtract 4:

5b = 20-4

5b = 16

We'll divide by 5:

b = 16/5 units

We'll substitute b in (2):

a + 16/5 = 20

We'll subtract 16/5:

a = 20 - 16/5

a = 84/5

Now, we'll calculate the area of the rectangle:

A = a*b

A = 84*16/5*5

A = 53.76 square units