I am confused with Following formulaes of combination..
1. n!/r!
2. n+k-1 C k
3. (P+1)*2^R where (P+R are total things and P are alike).
4. question such as number of ways of choosing 10 balls out of 15 balls in which 5 are red,8 are green,2 are black.
Anybody please provide me some reference to understand these formulaes related to combination.
in your question, 15 balls are divided in colours!
but i need to take 10 balls.and no condition is given on the colors of that 10 balls.
so i can take any color balls,
simply i have to choose 10 balls from 15 balls ,ehich is 15C10
identical balls will change the way to select ..
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