How do you evaluate 12P7?

1 Answer
Feb 16, 2017

color(white)(x)^12P_7=3991680x12P7=3991680

Explanation:

Perhaps you mean color(white)(x)^12P_7x12P7, which means

the number of ways one chooses a sample of 77 objects from a set of 1212 distinct objects, where order does matter and replacements are not allowed .

As color(white)(x)^nP_r=(n!)/((n-r)!)xnPr=n!(nr)!

and hence color(white)(x)^12P_7=(12!)/((12-7)!)x12P7=12!(127)!

= (12!)/(5!)=(12xx11xx10xx9xx8xx7xx6xx5xx4xx3xx2xx1)/(5xx4xx3xx2xx1)12!5!=12×11×10×9×8×7×6×5×4×3×2×15×4×3×2×1

= 12xx11xx10xx9xx8xx7xx6=399168012×11×10×9×8×7×6=3991680