Posted by **mysterychicken** 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] -
**Damon**, 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] -
**mysterychicken**, 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] -
**mysterychicken**, Thursday, June 25, 2009 at 6:22pm
..Oops just saw that Damon. Thanks!

-MC

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