Question:

Two unbiased dice are thrown. Then the probability that neither a doublet nor a total of 10 will appear is

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Using the complement rule $P(\text{Neither A nor B}) = 1 - P(A \cup B)$ is the most efficient way to solve "neither/nor" probability questions.
Updated On: Jun 4, 2026
  • $\frac{1}{12}$
  • $\frac{1}{36}$
  • $\frac{2}{9}$
  • $\frac{7}{9}$
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The Correct Option is D

Solution and Explanation

Step 1: Understanding the Question:
We need to calculate the probability of not getting a doublet and not getting a sum of 10 when rolling two dice.

Step 2: Key Formula or Approach:
Find the total number of outcomes. Find the number of outcomes for getting a doublet and getting a sum of 10. Subtract the union of these outcomes from the total to find the favorable outcomes, then divide by the total.

Step 3: Detailed Explanation:
Total possible outcomes when two dice are thrown $= 6 \times 6 = 36$.
Let $A$ be the event of getting a doublet: $A = \{(1,1), (2,2), (3,3), (4,4), (5,5), (6,6)\}$. There are 6 ways.
Let $B$ be the event of getting a total of 10: $B = \{(4,6), (5,5), (6,4)\}$. There are 3 ways.
The intersection $A \cap B$ (getting a doublet and a total of 10) is $\{(5,5)\}$, which is 1 way.
Using the principle of inclusion-exclusion, the total number of ways to get a doublet or a total of 10 is:
$$n(A \cup B) = n(A) + n(B) - n(A \cap B) = 6 + 3 - 1 = 8$$ The number of favorable outcomes (neither a doublet nor a total of 10) is $36 - 8 = 28$.
Required probability $= \frac{28}{36} = \frac{7}{9}$.

Step 4: Final Answer:
The required probability is $\frac{7}{9}$, matching option (D).
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