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A 5-digit security code has the numbers 1 through  7 to choose from. If each number can only be used once, how many different combinations are possible?

User JPvdMerwe
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The first position has 7 options to choose from, the second has 6, the third has 5, and so on. So the number of different arrangements is


_(7)P_(5)=5!\dbinom75=5!(7!)/(5!(7-5)!)=(7!)/(2!)=2520
User Toshiya
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