Subject: General Aptitude · Chapter: Probability · Exam: · Marks: · Difficulty:
Two dice are tossed. The probability that the total score is a prime number is
(a)$\frac{1}{6}$
(b)$\frac{1}{2}$
(c)$\frac{5}{12}$
(d)$\frac{7}{9}$
(e)None of these
Answer
Answer (as printed): C
Explanation
Clearly, $n(S)=(6 \times 6)=36$. Let $E$ be the event that the sum is a prime number. Then, $n(E)=\{(1,1),(1,2),(1,4),(1,6),(2,1),(2,3),(2,5),(3,2),(3,4),(4,1),(4,3),(5,2),(5,6),(6,1),(6,5)\}$. $\therefore n(E)=15$.
Explanation as extracted from the printed page; notation may be imperfect.