In mathematics we are often interested in **categorising** things, which we do by looking for common properties.

There are many ways to classify shapes. We can classify them based on:

- Number of sides;
- Number of vertices;
- Size of angles;
- Lines of symmetry.

What different shapes do you know based on the number of sides they have?

Thinking about only 3-sided shapes, how many different **special** 3-sided shapes do you know the names of? What are the properties of these shapes?

Thinking about only 4-sided shapes, how many different **special** 4-sided shapes do you know the names of? What are the properties of these shapes?

**Exercise**

Let’s try the short exercise of the first three questions on exercise 3J on page 54 (make sure to write the full sentence if a missing word is required):

The answers are below: