Part A
Answer: 720
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Work Shown:
6! = 6*5*4*3*2*1 = 720
The exclamation mark means factorial. You simply start with the given number 6 and count down til you get to 1. You multiply all of the numbers together.
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Part B
Answer: 6720
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Work Shown:
Use the nPr formula to get...
nPr = (n!)/((n-r)!)
8P5 = (8!)/((8-5)!)
8P5 = (8!)/(3!)
8P5 = (8*7*6*5*4*3!)/(3!)
8P5 = 8*7*6*5*4
8P5 = 6720
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Part C
Answer: 495
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Work Shown:
Use the nCr formula this time
n C r = (n!)/(r!(n-r)!)
12 C 4 = (12!)/(4!*(12-4)!)
12 C 4 = (12!)/(4!*8!)
12 C 4 = (12*11*10*9*8!)/(4!*8!)
12 C 4 = (12*11*10*9)/(4!)
12 C 4 = (12*11*10*9)/(4*3*2*1)
12 C 4 = (11880)/(24)
12 C 4 = 495