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10 questions from this quiz
Order doesn't matter in selections
3
6
n!r!(n−r)!\frac{n!}{r!(n-r)!}r!(n−r)!n!
8C3×5C3=560^8C_3 \times ^5C_3 = 5608C3×5C3=560
2n2^n2n
127127127
Sum of two numbers directly above it
nCr=n−1Cr−1+n−1Cr^nC_r = ^{n-1}C_{r-1} + ^{n-1}C_rnCr=n−1Cr−1+n−1Cr
(nr)\binom{n}{r}(rn)
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