In decimal, 4 digits ( 0  9) you can represent any number from 0000 to 9999. That is 10,000 unique number combinations. Incidentally, the number of unique cominations is 10 to the
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You have 10 choices for the first digit, then 10 choices
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You have 5 choices for the first number, 5 choices for the second,
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4 digits means less than 5 digits and greater than 3 digits. This eliminates all numbers greater than 9999 and all numbers less than 1000. How many numbers are there between 1000
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