📐 Angle Sum 📚 Grade 4 ⏱ 5 min
Sum of Angles in a Quadrilateral: 360 Degrees
After discovering the triangle's angle sum (180 degrees), it's natural to ask: what about a quadrilateral?
A quadrilateral is two triangles
Draw a diagonal in any quadrilateral — you get two triangles. Each has an angle sum of 180°, so together that is 180+180=360°.
💡 Check: a square has 4 angles of 90° each: 90×4=360 — matches the rule.
Practice
Three angles of a quadrilateral are 80°, 100°, 95°. What is the fourth? 360−80−100−95=85°.
FAQ
Does this rule work for any quadrilateral?
Yes, for any — a square, a rectangle, a trapezoid, even an irregular shape.