Probability
Variance of Difference of Two Dice
nta_pyq_2023_apr
Grade 12
Question:
Two dice A and B rolled. Variance of $\alpha-\beta$ is $\dfrac{p}{q}$ (coprime). Sum of positive divisors of $p$ is equal to
Step-by-Step Solution
Key Concept: $\text{Var}(\alpha-\beta)=\text{Var}(\alpha)+\text{Var}(\beta)=2\cdot\frac{35}{12}=\frac{35}{6}$. $p=35,q=6$.
$p=35$. Divisors sum $=1+5+7+35=48$.
Correct Answer: 3