Angles at a Point

Angles at a Point

Angles about a point add up to 360º (which is a complete circle).

360 degrees in a circle

If a point is on a straight line, then the angles on each side of the line add up to 180º.

180 degress on a straight line

Example 1

What is the value of the angle A in this diagram?

Given an angle of 140 degrees, what is the size of the other angle at a point

There are 360º in a circle. 140º has been allocated to one angle.

There are 360-140 = 220º left in the circle.

Answer: 220º

What is the value of the angle, B, in the diagram below?

Given four angles at a point: if three are known, what is the fourth?

Angles at a point add up to 360º.

Adding up the known angles: 30 + 130 + 60 = 220º.

Subtract from 360º: 360 - 220 = 140º.

Answer: 140º