A jar contains $3$ yellow marbles, $4$ red marbles, $10$ green marbles. and $4$ blue marbles. What is the probability that the first marble picked at random is blue and that the second marble is green and that the third marble picked is yellow, assuming that the marbles are put back into the jar after every time they are picked?
My attempt:
Probability the first marble is blue: $\frac{4}{21}$.
Probability the second marble is green: $\frac{10}{20} = \frac{1}{2}$
Probability the third marble is yellow: $\frac{3}{19}$
I don't think this is right though. Can someone help me please? Thank you.
Best Answer
You are decreasing the denominators of your fractions, but you shouldn't do that because you are putting the marbles back after each pick, so there are always 21 marbles in the jar.