A polygon has 1325 diagonals. How many vertices does it have?
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Answer / guest
The formula to find number of diagonals (D) given total
number of vertices or sides (N) is
N * (N - 3)
D = -----------
2
Using the formula, we get
1325 * 2 = N * (N - 3)
N2 - 3N - 2650 = 0
Solving the quadratic equation, we get N = 53 or -50
It is obvious that answer is 53 as number of vertices can
not be negative.
Alternatively, you can derive the formula as triange has 0
diagonals, quadrangel has 2, pentagon
has 5, hexagon has 9 and so on......
Hence the series is 0, 0, 0, 2, 5, 9, 14, ........ (as
diagram with 1,2 or 3 vertices will have 0
diagonals).
Using the series one can arrive to the formula given above.
| Is This Answer Correct ? | 11 Yes | 7 No |
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