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A polygon has 27 diagonals. The number of sides in the polygon is:

  • A.7
  • B.8
  • C.9
  • D.10

Answer: C

The formula for the number of diagonals is \(\frac{n(n-3)}{2}\).

\(\frac{n(n-3)}{2} = 27\)

\(n(n-3) = 54\)

We need two numbers with a difference of 3 that multiply to 54. By inspection, 9 and 6 satisfy this condition (9 × 6 = 54). Therefore, n=9. The polygon is a nonagon.

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