Question

a bag has 5 red marbles, 6 blue marbles and 4 black marbles. what is the probability of getting a blue marble, replacing it and getting another blue?

Answer 1

When you replace the marble, the second drawing is completely independent of the first one. That means you multiply the probabilities.

Answer 2

That means

p(drawing blue and then blue) = p(drawing blue) * p(drawing blue)

Answer 3

What is the probability of drawing a blue marble?

p(drawing blue) = (number of blue marbles)/(number of all marbles)