Mathematics 9709 · AS & A Level · Discrete random variables
Discrete random variables — practice question
A bag has 10 marbles: 4 are red and 6 are blue. Four marbles are drawn at random from the bag without replacement. The random variable $X$ represents the number of blue marbles drawn.
(a)[2]
Show that $\mathrm{P}(X = 2) = \frac{3}{7}$ from your working.
(b)[4]
Draw up a probability distribution table for $X$.
(c)[3]
Find the probability that at least 2 of the marbles chosen are blue, given that the selection includes at least 1 red marble and at least 1 blue marble.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A correct probability method for exactly two successes” …