Subject: General Aptitude · Chapter: Probability · Exam: · Marks: · Difficulty:
Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn has a number which is a multiple of 3 or 5?
(a)$\frac{1}{2}$
(b)$\frac{2}{5}$
(c)$\frac{8}{15}$
(d)$\frac{9}{20}$
Answer
Answer (as printed): D
Explanation
Here, $S=\{1,2,3,4, \ldots \ldots, 19,20\}$. Let $E=$ event of getting a multiple of 3 or $5=\{3,6,9,12$, 15, 18, 5, 10, 20\}. $$\therefore \quad P(E)=\frac{n(E)}{n(S)}=\frac{9}{20} .$$
Explanation as extracted from the printed page; notation may be imperfect.