Question

Here is a rectangle which has a width of x cm. x cm

The length of the rectangle is 8 cm longer than the width of the rectangle.
4 of these rectangles are used to make this 8-sided shape.
The perimeter of the 8-sided shape is 90 cm.
Work out the area of the 8-sided shape.

Answer 1

278.25 cm2

Explanation:

If the width of the rectangle is x (cm), as the length is 8cm longer, so that the length of the rectangle is: x + 8 (cm).

In the attached image, we can see the length of each side. Total length of the sides are 90 cm.

=> (x + x + 8) + x + 8 + (x+8) + (x + x + 8) + x + 8 + (x +8) = 90

=> 8x + 48 = 90

=> 8x = 90 - 48 = 42

=> x =42/8 = 5.25 (cm)

=> The width of the rectangle is 5.25cm

=> The length of the rectangle is: 5.25 + 8 = 13.25 cm

=> The area of one rectangle is: Length x Width = 5.25 x 13.25 = 69.5625 cm2

As the 8-sided shape is made from 4 rectangles, so that:

Area of 8 sided shape = 4 x Area of the rectangle = 4 x 69.5625 = 278.25 cm2