Probability
Probability
nta_abhyas_2025
Grade 12
Question:
2 coins can be both 10 rupee coin, both 5 rupee coins or one 5 rupee coin and one 11 rupee coin. Expected value = $\frac{20}{1} + \frac{x}{10} + \frac{20+25}{3} = 15$.
Step-by-Step Solution
Key Concept: Expected value is computed as the sum of (value × probability) across all outcomes
The expected value calculation involves three cases with probabilities. Setting up: $\frac{20}{1} + \frac{x}{10} + \frac{45}{3} = 15$ and solving for the weighted average yields $x = 20$. The calculation uses the linearity of expectation across the distinct coin combinations.
Correct Answer: 20