CBSE 2022 · Region 2 · Set 1 · Q4 · 2 marks
A pair of dice is thrown. It is given that the sum of numbers appearing on both dice is an even number. Find the probability that the number appearing on at least one die is 3.
Marking-scheme solution
A: number appearing on at least one die is $\displaystyle 3$
B: sum of numbers appearing on both dice is even
Clearly, \(\displaystyle A \cap B=\{(3,1),(3,5),(1,3),(5,3),(3,3)\}\)
\[\begin{aligned}
P\left(\frac{A}{B}\right)=\frac{P(A \cap B)}{P(B)} & =\frac{5 / 36}{18 / 36} \\
& =\frac{5}{18}
\end{aligned}
\]
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CBSE Class 12 Mathematics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.