Question

You draw two marbles from a bag containing 3 red marbles and 6 blue marbles what is the probability that both marbles are red

Answer 1

Probability = favorable cases / total cases
favorable cases = choose 2 balls out three red balls = \[\left(\begin{matrix}3 \\ 2\end{matrix}\right) = 3\]

Total cases = choose 2 balls out of all 6 balls = \[\left(\begin{matrix}6 \\ 2\end{matrix}\right) = 15\]

Probability = 3/15 = 1/5

Answer 2

Total cases should be 2 balls out of 9 balls:
\(\left(\begin{matrix}9 \\ 2\end{matrix}\right) = 36\)

Answer 3

@Vincent-Lyon.Fr Oh yes! Total cases should be 36.Thanks
So the probability is 1/12. .