Multiple choice

a pair of dice is rolled together til la sum of either 5 or 7 is obtained. Then the probability that 5 comes before 7 is...........

  1. 0.4

  2. 0.6

  3. 0.5

  4. None of these
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A Correct answer
Explanation

P(sum=5) = 4/36 = 1/9. P(sum=7) = 6/36 = 1/6. We want the probability of 5 before 7, which is P(5) / (P(5) + P(7)) = (1/9) / (1/9 + 1/6) = (1/9) / (5/18) = 2/5 = 0.4.

AI explanation

A sum of 5 can be obtained in 4 ways, while a sum of 7 can be obtained in 6 ways, out of 36 total outcomes. Using the conditional probability of stopping at either sum, the chance that the stopping sum is 5 is 4 divided by the sum of 4 and 6. This gives a probability of 4/10, which equals 0.4.

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