A die is thrown three times and the sum of the three numbers is found to be 15. The probability that the first throw was a four is
Question and options
A die is thrown three times and the sum of the three numbers is found to be 15. The probability that the first throw was a four is
Answer and explanation
Correct answer: C - \(\frac{1}{5}\)
Outcomes summing to 15: same as (7-a)+(7-b)+(7-c) = 6, giving C(5,2) = 10. With first = 4, the rest sum 11: (5,6),(6,5) = 2. Probability 2/10 = 1/5.
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IPMAT Indore
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