# Perimeter of rectilinear shapes

## In a nutshell

The perimeter of a rectilinear figure is the full distance measured around a square or rectangle and can be calculated by adding all the side lengths together. You may have to measure the side lengths, the lengths may be stated or shown on a centimeter square grid.

## How to work out the perimeter of a square

#### Procedure

1 | Find the length of one side, by measuring with a ruler, looking for a given length, or counting squares on a centimetre grid. |

2 | As all the sides are the same length in a square, find the perimeter by multiplying the side length by four. |

##### Example 1

*Find the perimeter of the square.*

*The square is given on a centimetre grid. Count the squares to find the side length. There are four squares, so the length of each side is $4cm$. The perimeter can be calculated by multiplying the side length by four.*

*$Perimeter = 4 \times 4 = \underline{16cm}$*

## How to work out the perimeter of a rectangle

#### PROCEDURE

1
| Find the length and the width, by measuring with a ruler, looking for a given length, or counting squares on a centimetre grid. |

2 | As opposite sides are the same length in a rectangle, find the perimeter by adding two lengths and two widths together. |

##### Example 2

*Find the perimeter of the rectangle.*

*The rectangle is given on centimetre square grid, so count squares to find the length and width.*

*$Length = 5cm, \space width = 3cm$*

**

*Calculate the perimeter*

*$Perimeter = 5+5+3+3=\underline{16cm}$*

**

##### Example 3

*Find the perimeter of the rectangle.*

*The lengths are already given, so find the perimeter by adding the side lengths up.*

*$Perimeter = 7+7+4+4=\underline{22cm}$*