Question

The number of pairs of diagonals of a regular polygon of $10$ sides that are parallel, are

Answer 1

Answer: 45

$\underset{\text{No. of ways to select a verex}}{{}^5{C}_1}\times \underset{\text{No. of ways to select a pair }}{{}^4{C}_2}=30$

$=3C_2\times 5=15$
$\therefore$ Ans. $=45$