What is the formula to get 4 digit combinations from numbers 0-9?

1 Answer
Lil Del
Oct 17, 2016

Please read the explanation, because the answer is either #10,000# or #5,040#.

Explanation:

Since there are #10# choices for each digit, the number of #4#- digit combinations is given by
#10*10*10*10 = 10,000#,

UNLESS using a digit means it cannot be used again. In that case, the number of #4#-digit combinations is given by
#10*9*8*7 = 5,040#.

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