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magical cook
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There are two ways you can solve this question
One is the dependant probability format.
If two non defective pens have to be selected, the probability of selecting first one is 9/12 and the probability of selecting the second one is 8/11.
9/12 x 8/11 = 6/11
The second method is using the hypergeometric probability formula which is (number of favourable events)/(total number of events).
number of favourable events = 9C2
total number of events = 12C2
9C2/12C2 = 6/11
