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					 A polygon has 44 diagonals the number of its sides is ?
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                        - 9
- 10
- 11
- 12
 
Correct Option: C
Let  there be n sides of the polygon. Then  it has n vertices. 
The total number of straight lines obtained by joining  n vertices by talking 2 at a time is nC2
 These nC2 lines also include n sides of polygon. 
Therefore, the number of diagonals formed is nC2 - n. 
Thus,  nC2 - n = 44
⇒  [n(n - 1)/2] - n = 44
⇒  ( n2 - 3n) / 2  = 44
⇒ n2 - 3n = 88 
⇒  n2 - 3n - 88 = 0 
⇒(n - 11) (n + 8)  = 0 
∴  n = 11 
 
 
	