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Posted by on Thursday, June 25, 2009 at 6:05pm.

Need help with these-

1.How many groups of 4 fabrics can be selected from 7 fabrics?

2.The school photographer wants to photograph 3 students from a club with 14 members. How many combinations can be made?

3.Philip wishes to check 2 books out of his school library. If the library contains 800 books, in how many ways might Philip make his choice of books?

Thanks
-MC

  • Pre-Algebra [Combinations] - , Thursday, June 25, 2009 at 6:21pm

    C(n,k) = n!/[ (n-k)!k! ]
    for example if n = 7 and k = 4
    C(7,4) = 7! /[ 3! 4! ]
    = 7*6*5 *4! /[3*2*1 *4!]
    4! cancels top and bottom
    6 cancels top and bottom
    = 7*5
    =35

    Now try n = 14, k = 3
    and n = 800, k = 2

  • Pre-Algebra [Combinations] - , Thursday, June 25, 2009 at 6:21pm

    Nevermind I got all the answers:
    1. 35 groups
    2. 364 combinations
    3. 319,600 choices

    -MC

  • Pre-Algebra [Combinations] - , Thursday, June 25, 2009 at 6:22pm

    ..Oops just saw that Damon. Thanks!
    -MC

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