How many diagonals are there in a decagon ........

Quantitative Aptitude ( CCS) Permutation & Combination

How many diagonals are there in a decagon?

None of the above

A diagonal joins a vertex to one of the vertices that do not include that vertex itself and the immediately adjacent vertices.

So, for each vertex there are seven diagonals.

Times 10 equals 70; each diagonal is counted twice, so the final answer is 35.

Hence, option 3 is the correct answer.

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