Quadrilaterals & polygons
Angle sums, regular polygons and kinds of quadrilaterals.
Learn with Kutty
Go one screen at a time. Press Next when you are ready. Tap 🔊 Read to me to listen.
Cut a polygon into triangles to find its angles.
Look: A hexagon (6 sides) cuts into 4 triangles.
✏️ Your turn!
Type your answer and press Check. Kutty will tell you if it is right.
1Angles of a pentagon add to?
2Each angle of a regular hexagon?
3A quadrilateral has 80°, 95°, 110°. The fourth?
! Careful!
✗Using n × 180°.
✓It is (n − 2) × 180°.
✗A square’s angles add to 720°.
✓2 triangles: 360°.
See the whole lesson on one page
Cut a polygon into triangles to find its angles.
A shape with n sides makes n − 2 triangles. So its angles add up to (n − 2) × 180°.
Think of it like thisFrom one corner, cut the shape into triangles like pizza slices. Each triangle holds 180°.
Solved together
A regular octagon has 8 equal angles. How big is each?
8 sides make 8 − 2 = 6 triangles.
6 × 180° = 1080°Share among 8 equal angles.
1080 ÷ 8 = 135
AnswerEach angle is 135°.
Now practise it
Kanakku makes new questions on quadrilaterals & polygons every time. It shows the working and gives a hint when you are stuck.