Question

20 tickets on which numbers 1 to 20 are written are mixed thoroughly and then a ticket is drawn at random out of them. Find the probability that the number on the drawn ticket is a multiple of 3 or 7.

Answer 1

$n\left(s\right)=20$, Multiples of $3or7,A:\{3,6,9,12,15,18,7,14\},n\left(A\right)=8$
$\therefore$ Required probability $=\frac{8}{20}or\frac{2}{5}$