Tuesday, 12 July 2011
1. Combinations without Repetition This is how lotteries work. The numbers are drawn one at a time, and if you have the correct numbers (no matter what order) you win!
Using a pool ball example, let us say that you just want to know which 3 pool balls were chosen, not the order. We already know that 3 out of 16 gave us 3,360 permutations.
Pascal's Triangle
You can also use Pascal's Triangle to find the values. Go down to row "n" (the top row is 0), and then along "r" places and the value there is your answer. Here is an extract showing row 16:
1 14 91 364 ...
1 15 105 455 1365 ...
1 16 120 560 1820 4368 ...
http://www.mathsisfun.com/combinatorics/combinations-permutations.html
i dont really understand this but may be you will so read and see tmr we can discuss
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