A teacher is making her students do the attendance. She has 3 blue ink pens and 9 black ink pens. The put the pen back every time it is used. What is the probability that the first three students will consecutively pick a blue ink pen?
We have 12 pens in total
P(first three pens are blue with replacement) = 3/12 * 3/12 * 3/12 =
(1/4) * (1/4) * (1/4) =