16Hit1600
Geometry and TrigonometryVery hardNumber of sides from the interior angle sum

Geometry and Trigonometry practice question

The sum of the interior angles of a polygon is 1,440°. How many sides does the polygon have?

Answer: 10

(n − 2) × 180 = 1,440 → n − 2 = 8 → n = 10.

Common wrong answers

If you answered 8
8 is n − 2.
If you answered 9
9 comes from an arithmetic slip; 1,440 ÷ 180 = 8.
If you answered 12
12 comes from adding 2 twice.

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