DAT Math Destroyer Question

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schulc76

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I'm having trouble understanding what the P and ! means in the Probability and Combinatrics problems. On practice test 1, question 14 "In how many different ways (orders) can 5 people stand in line?
The answer is 120 with the reason being: P(5,5)=5!=120

Could someone explain this one to me? I'd really appreciate it.

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! just means multiply the number by all the positive numbers smaller than it:
5 x 4 x 3 x 2 x 1 = 120 :)
 
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