Angle facts

About 1 min to read, then 7 practice questions

The facts

Angles on a straight line add up to 180°.
Angles round a point add up to 360°.
Vertically opposite angles (where two straight lines cross) are equal.
Angles in a triangle add up to 180°. An isosceles triangle has two equal base angles.

Here x = 180 − 50 − 60 = 70°.

If the angles on a line are 3x and (2x + 30)°, then 3x + 2x + 30 = 180, so 5x = 150 and x = 30.

Check: 90 + 90 = 180.

Answering from memory soon after reading is what makes it stick, so now is a good time.

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