#16
Top 50 Mistake
Using 180° as the sum for all polygons
"The Triangle Default"
The Mistake in Action
Find the sum of interior angles in a hexagon.
Wrong: $180°$
Why It Happens
Students remember that angles in a triangle sum to $180°$ and incorrectly apply this to all shapes.
The Fix
The sum of interior angles = $(n - 2) \times 180°$
For a hexagon, $n = 6$: $$(6 - 2) \times 180° = 4 \times 180° = 720°$$
Memory aid: A hexagon can be split into 4 triangles (draw lines from one vertex), and $4 \times 180° = 720°$.
Spot the Mistake
Can you identify where this student went wrong?
Find the sum of interior angles in a hexagon.
Sum = $180°$
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: