A box contains 8 green and 4 blue marbles. Two
marbles are selected (at once with no replacement).
Find the expected number of green marbles among
the selected ones.
(a) 1
(b) 1/3
(c) 2/3
(d) 1/2
(e) 4/3
(f) none of the above

Question

A box contains 8 green and 4 blue marbles. Two
marbles are selected (at once with no replacement).
Find the expected number of green marbles among
the selected ones.
(a) 1
(b) 1/3
(c) 2/3
(d) 1/2
(e) 4/3
(f) none of the above

perl · Answer

you want probability of getting two greens in a row

8/12 * 7/11

anonymous · Answer

I've done that much

anonymous · Answer

I just don't know how to get the final answer

perl · Answer

the phrase 'expected number' is a bit confusing

anonymous · Answer

My professor has the answer listed as E, 4/3, and I'm not able to get that

perl · Answer

ok i think i see what he did

anonymous · Answer

What did you do there? I'm really confused

perl · Answer

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