Two fair dice are thrown. What is the probability that the sum of the numbers is ?
Answer and explanation
Correct answer: B. 1/18
- Step 1: The sample space for rolling two six-sided dice contains equiprobable outcomes with .
- Step 2: List the outcomes satisfying : (5, 6), (6, 5), which yields pairs.
- Step 3: Calculate the probability: .
Answer
1/18.
Why not the others: 1/36 assumes only a single outcome yields the required dice sum; 1/12 is the probability of obtaining a sum of or (); 1/6 assumes a uniform distribution over all possible sums.
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