The interior angles of a pentagon are 2x 5 o x ... - WAEC Mathematics 2009 Question
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 option: c
(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
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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