SOLUTION: A box contains six red pens and three blue pens. (a) A pen is selected at random, the colour is noted and the pen is not returned to the box. This procedure is performed a second,

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Question 1062257: A box contains six red pens and three blue pens. (a) A pen is selected at random, the colour is noted and the pen is not returned to the box. This procedure is performed a second, then a third time.(a) Find the probability of obtaining (i) three red pens, (ii) two red pens and one blue pen, in any order, (iii) more than one blue pen.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Three red pens,
P=%286%2F9%29%285%2F8%29%284%2F7%29=5%2F21
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Look at the possible outcomes,
RRB
RBR
BRR
There are three of them so,
P=3%286%2F9%29%285%2F8%29%283%2F7%29=15%2F28
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We'll do this one backwards.
Find the probability of no blue pens or only one blue pen,
No blue pens would be all red from above, P=5%2F21
One blue pen would be the second answer, P=15%2F28
So then no blue pens or one blue pen would be,
P=5%2F21%2B15%2F28=20%2F84%2B45%2F84=65%2F84
So then the complement of that probability is your answer,
P=1-65%2F84=84%2F84-65%2F84=19%2F84