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Location: 4.2 Factorials and Permutations
Discussion: Stuck
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r_potter |
Stuck
Feb 4 2009, 11:14 PM EST
Hi, I'm doing the same work in my class, but I'm stuck on how one of the questions:How many ways can you pick a president, vice-president, and secretary from a group of six boys and five girls if: b) there must be at least one boy chosen? and c) there must be only one girl chosen? I already have the answers here, but I do not understand the steps I must take to get to the answer. If you could help me, that would be appreciated! Do you find this valuable? |
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Posted Anonymously |
1. RE: Stuck
Feb 5 2009, 10:11 PM EST
Hey,kk so i think this would be a matter of combinations, and the words " AT LEAST" hint that its going to be a Total - None situation, which is really the easiest way to do these types of problems..... so total possibilities (11 choose 3)= 165 i think....and then subtract it by ( no boys ) which is ( 6 choose 0 ) ( 5 Choose 3 ) ...that should give you 10..... 165 - 10 = 155 should be the possibilities.... THEN for the next part....only one girl chosen.... simply ( 5 choose 1 ) ( 6 choose 2) = 75 Hope it helped ! Do you find this valuable? |
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Posted Anonymously |
2. RE: Stuck
Feb 18 2009, 8:50 PM EST
6 boys5 girls 11 total B) Total ways of performing the task: 11P3 = 990 Opposite ways of performing the task : 5P3 = 60 Total (990) - opposite (60) = 930 ways of picking at least one boy C) Total ways of performing the task: 11P3 = 990 Opposite ways of performing the task : 6P3 = 120 Total (990) - opposite (120) = 870 ways of picking at least one girl 2 out of 2 found this valuable. Do you? |
