The interior angles of a pentagon are (2x + 5)o, (x + 20)o, xo, (3x…

The interior angles of a pentagon are (2x + 5)o, (x + 20)o, xo, (3x – 20)o and (x + 15)o. Find the value of x
  • A.
    80o
  • B.
    70o
  • C.
    65o
  • D.
    40o
Correct Answer: Option C
Explanation

(2x + 5)o + (xo + 20o) + x + (3x – 20)o + (x + 15)o = (n – 2) x 180
8n + 20 = (5 – 2) x 180
where n = 5(Pentagon)
8n + 20 = 3 x 180
8n + 20 = 540
8n = 540 – 20
8n = 520
x = 65o

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