Subject
Quantitative Aptitude
Topic
Probability
A dice is rolled three times and sum of three numbers appearing on the uppermost face is 15. What is the chance that the first roll was four?
A dice is rolled three times and sum of three numbers appearing on the uppermost face is 15. What is the chance that the first roll was four?
ক)
1/216খ)
2/69গ)
1/5ঘ)
3/71ঙ)
None of theseExplanation
As per the condition given in the question: All the combinations of outcomes for getting a sum of 15 on the uppermost face are: ⇒ (4, 5, 6), (5, 4, 6), (6, 5, 4), (5, 6, 4), (4, 6, 5), (6, 4, 5), (5, 5, 5), (6, 6, 3), (6, 3, 6), (3, 6, 6) ⇒ n(S) = 10 Now, outcomes on which first roll was four are n(E) = (4, 5, 6), (4, 6, 5) Therefore required probability P(E): ⇒ P(E) = n(E)/n(S) = 2/10 = 1/5 Hence, the required probability is 1/5.Related questions
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