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Wednesday, October 3, 2007

A-Math P & C Clarification

lijun(: said...
hey. i just want to clarify something that i'm not very sure of.

is nCr x r! = nPr ??


By definition,

nCr = nPr/r!

Well, I never remember this 'rule'
For example, find the number of ways to form a 3 letter word from a,b,c,d,e

Student #1:
5C1*4C1*3C1

Student #2:
5P3

Both answers are correct though different approaches are taken, so no need to remember the 'rule'

:)

1 comments:

lijun(: said...

ok. thanks! (: