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Subject :IMO    Class : Class 8

The sum of the interior angles of a polygon is 1440°. Find the number of sides of the polygon.

A14
B12
C10
D5


Can you please clarify the answer

Ans 1:

Class : Class 8
it would be 10. [n-2]180=1440 180n-360=1440 180n=1800 n=1800/180 = 10

Ans 2:

Class : Class 8
the answer should be 10 because= (n-2)*180=1440

Ans 3:

Class : Class 10
Answer: C

Solution
If a polygon has 'n' sides, then it is divided into (n – 2) triangles. The sum of the angles of a triangle = 180°. Therefore, the sum of interior angles of a polygon having n sides is (n – 2) x 180.
(n - 2) x180 = 1440
n - 2 = 1440/180 = 8
n = 8 + 2 = 10

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