Compound shapes
Sometimes shapes can be more complicated. Be particularly careful to add up the lengths of every side when you work out the total perimeter.
Perimeter \(= 2 + 2 + 3 + 3 + 5 + 5 = 20~cm\)
In some cases you’ll need to calculate the 'missing' lengths, eg \(x\) and \(y\) in the question below.
Question
A plan of a play area is shown below:
a) Calculate the length of \(x\) and \(y\).
b) Calculate the perimeter of the play area.
a) The length of the play area is \(20~m\), so \(x = 20 - 8 = 12~m\).
The width of the play area is \(15~m\), so \(y = 15 - 5 = 10~m\).
b) Perimeter \(= 8 + 5 + 12 + 10 + 20 + 15 = 70~m\).
