How many different numbers can be formed by taking one, two, three, and four digits from the digits 1, 2, 7, 8, if repetition are not allowed ? Please Help
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I just tried this again, and i got the answer 64, am I correct ???
Originally Posted by creatively12 How many different numbers can be formed by taking one, two, three, and four digits from the digits 1, 2, 7, 8, if repetition are not allowed ? Using the notation $\displaystyle _N\mathcal{P}_k=\frac{N!}{(N-k)!}$ the answer is $\displaystyle \sum\limits_{k = 1}^4 {_4 \mathcal{P}_k } $.
Thanks for the reply so my answer is correct right ???
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