Maths · Rung 24 of 30

Angles and theorems

Two crossing lines make opposite angles that are equal and adjacent angles that add up to 180°. A transversal across two parallels repeats the same angle at both: the corresponding angles. In a triangle, the exterior angle at a vertex equals the sum of the two interior angles that do not touch it.

Where this sits

This is where the ladder starts: nothing is needed before it.

Exercises from this rung

Generated by the app, from easiest to hardest

  1. How big is angle x?

    • 70°
    • 250°
    • 110°
    • 90°

    Why Adjacent angles on a straight line add up to 180°: x = 180 − 110 = 70°.

    easier

  2. What do the interior angles of a pentagon add up to?

    Answer 540

    Why From one vertex you get 3 triangles, each adding up to 180°: (5 − 2) × 180 = 540°.

    harder