document.write( "Question 247087: A box contains 3 red and 5 green marbles. If 3 marbles are drawn without replacement, what is the expected number of red marbles? \n" ); document.write( "

Algebra.Com's Answer #180312 by edjones(8007) $\"\"$ $\"About$

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nCr=n!/((n-r)!r!) Combination of n things r at a time.
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\n" ); document.write( "If 56 draws of 3 marbles are done these are the expected results.
\n" ); document.write( "3 red: 3C3 = 1
\n" ); document.write( "2 red & 1 green: 3C2 * 5C1 = 15
\n" ); document.write( "1 red & 2 green: 3C1 * 5C2 = 30
\n" ); document.write( "3 green: 5C3 = 10
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