# CBSE Class 12-science Maths Probability

- there are 4 cards numbered 1 to 4 one number on one card . 2 cards are drawn at random without replacement . let x denote the sum of numbers on the 2 drawn cards . find the mean and varience of x
- Four bad eggs are mixed with 10 good ones . three eggs are drawn one by one without replacement. Let X be the no of bad eggs drawn . Find the mean and variance of X.
- A box contains 16 bulbs , out of which 4 bulbs are defective. Three bulbs are drawn at random from the box. Let X be the no of defective bulbs drawn . find the mean and variance of X
- What is the mean of a random variable
- Define variance and standard deviation of a random variable.
- Find the mean of the number obtained on a throw of an unbiased dice
- Two dice are thrown simultaneously. If X denotes the number of sixes, find the variance of X.
- In a meeting, 70% of the members favour and 30% oppose a certain proposal. A member is selected at random and we take X = 0 if he opposed, and X = 1 if he is in favour. Find E(X) and Var(X).
- Let a pair of dice be thrown and the random variable X be the sum of the numbers that appear on the two dice. Find the mean or expectation of X.
- A bag contains 4 black and 3 red balls. Let X be the random variable of red balls. Find the mean and variance of the random variable X, if three balls drawn successfully with replacement.