📐 Angle Formula Practice 📚 Grade 4-5 ⏱ 6 min
General Polygon Angle Formula: Practice
After learning the formula (sides minus 2) times 180 degrees, practice locks in the pattern across different polygon shapes.
Practice with different polygons
Heptagon (7 sides): (7−2)×180=900°
Octagon (8 sides): (8−2)×180=1080°
Decagon (10 sides): (10−2)×180=1440°
Working backward from the sum
A polygon's angles sum to 720°. How many sides does it have? 720÷180=4, plus 2 = 6 sides — a hexagon.
FAQ
Why practice this beyond grade 4?
It builds algebraic thinking — working the formula both forward and backward strengthens flexible problem solving.