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Everyday maths 1 (Wales)

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# 3.1 Measuring the perimeter of irregular shapes

## Example: How to measure the perimeter of an irregular shape

How would you measure the perimeter of an irregular shape – an L-shaped room, for instance – if you didn’t have all of the measurements that you would need? Watch the following video to find out.

Download this video clip.Video player: 19_ani_irregular_shapes.mp4

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Now try the following activity. Remember to check your answers once you have completed the questions.

## Activity 8: Finding the perimeter

Note that you can assume that all of the corners in the images in this activity are right angles.

1. A gardener decides to lay a new path next to his lily pond. The drawing shows the dimensions of the path.
Figure 18 A pathway

The gardener decides to paint a white line around the perimeter of the path. What is the perimeter of the path?

2. A tourist information centre has a new extension.
Figure 19 A new extension

The tourist board wants to attach a gold strip around the border of the floor of the building. What is the perimeter of the new extension?

### Answer

1. To calculate the missing sides you should have carried out the following calculations:

• 14 – 3 = 11
• 15 – 1.5 = 13.5

Now that you have found the missing sides, you can add them all together:

• 15 + 14 + 1.5 + 3 + 13.5 + 11= 58 m
2. To calculate the missing sides you need to carry out the following calculations to calculate the perimeter:

• 5 – 2 = 3
• 6 – 2 = 4

Now that you have found the missing sides, you can add them all up together to calculate the perimeter:

• 6 + 3 + 3 + 1 + 1 + 2 + 2 + 4 = 22 m

## Summary

In this section you have learned how to work out the perimeter of both simple and irregular shapes.