Two dice are thrown. What is the probability that the sum of numbers on two dice are 9 or numbers on two dice are prime numbers?
Two dice are thrown. What is the probability that the sum of numbers on two dice are 9 or numbers on two dice are prime numbers? Correct Answer 13/36
Given:
Two dice are rolled then,
Number of outcomes = 36
Calculation:
Outcomes when sum of numbers on two dice is 9 =
= {(3,6), (4, 5), (5, 4), (6, 3)}
= 4
Probability when sum of numbers is 9 = 4/36 = 1/9
Outcomes when two numbers are prime =
= {(2,2), (2,3) (2,5), (3,2), (3,3), (3,5), (5,2), (5,3), (5,5)}
= 9
Probability that two numbers are prime numbers =
= 9/36 = ¼
Required probability = 1/9 + ¼ = 13/36
Tricks:
Maximum sum of numbers on two dice = 12
Total number of prime numbers in a die = (2, 3 and 5) = 3
Total outcomes that two numbers are prime numbers = 3 × 3 = 9
Required probability = 9/36 = 1/4
মোঃ আরিফুল ইসলাম
Feb 20, 2025


