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In how many ways can five balls be chosen and so that

(a) two are blood-red and 3 are black?
(b) three are red and two are blackness?

out of $7$ blackness and $viii$ red

Should I use permutation? or $8\times7\times7\times6\times5$?

And why?

asked Dec 4 2013 at 3:53

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4

  • $\begingroup$ the question is incomplete , 5 assurance be called out of what ? $\endgroup$

    Dec 4 2013 at 3:56

  • $\begingroup$ How many balls are at that place of each color? $\endgroup$

    Dec 4 2013 at three:58

  • $\begingroup$ @Jeremy viii cherry-red 7 black $\endgroup$

    December four 2013 at 4:00

  • $\begingroup$ @TrafalgarLaw viii red 7 black $\endgroup$

    Dec 4 2013 at 4:01

1 Answer one

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You lot dont need to apply permutation hither because the ordering is not of import .

You will have to cull combination here .

choosing $2$ scarlet out of $8$ red = $_8C_2$ ways choosing $3$ black out of $7$ black = $_7C_3$ ways

therefore full number of means of doing (a)= $_8C_2 * _7C_3$

answered December 4 2013 at 4:07

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3

  • $\begingroup$ THANKS! i got 980 is that right? $\endgroup$

    Dec 4 2013 at 4:19

  • $\begingroup$ and so permutation is when gild matters and combination when society does non matter? $\endgroup$

    Dec four 2013 at 4:twenty

  • $\begingroup$ it should be correct $\endgroup$

    December 4 2013 at 4:20

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