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A drawer contains exactly 5 red, 4 blue and 3 green pencils. if two of the pencils are selected at random one after the other without replacing the first, what is the probability that the first one is red and the second one is green?

Answer 1

#5/44#

There are initially #12# pencils with #5# red and #3# green.

#P("first pencil is red")= 5/12#

If the first pencil is red and is not replaced, #11# pencils remain of which #3# are green #P("second pencil is green given first pencil is red") = 3/11#

#P("first pencil is red and second pencil is green")= 5/12xx3/11 = 5/44#

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Answer 2

Eva Abramson

The probability that the first pencil selected is red and the second one is green is (5/12) * (3/11) = 15/132 or approximately 0.1136.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.