An angle is made when $2$2rays (lines) meet at a common point or vertex.

We measure the size of angles with reference to a circle with a centre at the common vertex. An angle that turns through $\frac{1}{360}$1360 of a circle is called a "one-degree angle".

That means that if we have a number of one-degree angles, we can add then together to find the total size of that angle. For example, an angle that turns through $12$12 one-degree angles would have an angle measure of $12^\circ$12°. The angles in a circle add up to $360$360 degrees.

If we know that the angles in a circle add up to $360$360 degrees we can work out the values of unknown angles in a circle. Look at this demonstration to see how.