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 if $3$ or $5$.

Answer 1

Probability of drawing multiple of $3=\frac{6}{20}$

Probability of drawing multiple of $5=\frac{4}{20}$

Probability of drawing multiple of $15=\frac{1}{20}$

Total Probability $=\frac{6}{20}+\frac{4}{20}-\frac{1}{20}=\frac{9}{20}$