Angles · Usually met around P6
Angles on a straight line and around a point
Line 180°, point 360°, right angle 90°.
How to do it
Method
Line 180°, point 360°, right angle 90°
130 + 150 = 280, 360 − 280 = 80
Another way
Take each away
360 − 130 − 150 = 80
In full
Use what the angles add up to. Angles on a straight line (a straight angle) make 180°, angles round a point (a full turn) make 360°, and a right angle is 90°. So x is the total minus the angles you know: 50° on a straight line, 180 − 50 = 130, x = 130°. Quicker: add the known angles first, then take them away in one go. 130° and 150° round a point: 130 + 150 = 280, 360 − 280 = 80, x = 80°. Another way is to take the known angles away one by one: 360° − 130° − 150° = 80°.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
∠x = ?°
Show the answer and working
Answer: ∠x = 35°
A right angle is 90°: 90 − 55 = 35, so x = 35°
Example 2
∠x = ?°
Show the answer and working
Answer: ∠x = 24°
A right angle is 90°: 90 − 66 = 24, so x = 24°
Example 3
∠x = ?°
Show the answer and working
Answer: ∠x = 50°
Angles on a straight line make 180°: 180 − 130 = 50, so x = 50°
Practise it in the game →Angles · Free to start, unlimited questions, no download