Q. If three of the six vertices of a regular hexagon are chosen at random, then the probability that the triangle formed with these chosen vertices is equilateral is :
Solution:
Only two equilateral tringles are possible $A_1 A_3 A_5$ and $A_2A_5A_6$
$\frac{2}{6_{C_3}} = \frac{2}{20} = \frac{1}{10}$
