a) 5
b) 10
c) 8
d) 7
Answer: a
Explanation: A pentagon has 5 sides. We obtain the diagonals by joining the vertices in pairs.
Total number of sides and diagonals,
= 5C2
= $$\frac{{5 \times 4}}{{2 \times 1}}$$
= 5 × 2 = 10
This includes its 5 sides also.
⇒ Diagonals = 10 – 5 = 5
Hence, the number of diagonals
= 10 – 5
= 5
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