.
The number of ways to choose 3 things from the set of 5 things is
= = = = cancel 3! = 1*2*3 in both the numerator and denominator = = = 10.
In general case, the number of ways to choose "m" things from the set of "n" things (n > m) is
= = = .
It is called the "number of combinations of n items taken m at a time".
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On combinations, see the lessons
- Introduction to Combinations
- PROOF of the formula on the number of Combinations
- Problems on Combinations
- OVERVIEW of lessons on Permutations and Combinations
in this site.
Also, you have this free of charge online textbook in ALGEBRA-II in this site
- ALGEBRA-II - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Combinatorics: Combinations and permutations".
Save the link to this textbook together with its description
Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson
into your archive and use when it is needed.