The angles of a pentagon are in arithmetic progression. One of the angles, in degrees, must be:
Explanation:
The sum of interior angles of a pentagon = 540°
Let the angles of the pentagon be a – 2d, a – d, a, a + d, a + 2d
∴ a – 2d + a – d + a + a + d + a + 2d = 540
∴ 5a = 540
∴ a = 108°
∴ One of the angles must be 108°.
Hence, option (a).
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