JEE Main 2024 Mathematics question
Three balls are drawn at random from a bag containing 5 blue and 4 yellow balls. Let the random variables X and Y respectively denote the number of blue and yellow balls. If and are the means of X and Y respectively, then 7 + 4 is equal to .
Answer: 17
Solution
= 3 × 5/9 = 5/3 and = 3 × 4/9 = 4/3, so 7(5/3) + 4(4/3) = 51/3 = 17.