SOLUTION: A pen holder holds ten pens, three of which do not write. If three pens are selected at random, find the probability that at least one (a)writes and (b) doesnt write?

Question 665650: A pen holder holds ten pens, three of which do not write. If three pens are selected at random, find the probability that at least one (a)writes and (b) doesnt write?
Answer by DrBeeee(684) (Show Source): You can put this solution on YOUR website!
I'm not an expert on this, but I'll give you an answer and maybe one of the other tutors can comment/correct it.
I say that the
(1) P(at least one writes) = 1 - P(none write) or
(2) P(at least one writes) = 1 - (3/10)(2/9)(1/8)
(3) P(at least one writes) = 119/120
The
(4) P(at least one doesn't write) = 1 - P(all write)
(5) ditto = 1 - (7/10)(6/9)...(1/4)
(6) P(at least one doesn't write) = 119/120
Sorry, no guarantees.

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