HELP!!

[prowannabie]

Im not good with math, can someone explain to me how u get this answerignore the dots on left, only way i could get it to indent


. 2
C =1081
. 47

[BruceZ]

[ QUOTE ]
Im not good with math, can someone explain to me how u get this answerignore the dots on left, only way i could get it to indent


. 2
C =1081
. 47

[/ QUOTE ]

C(47,2) or 47c2 = 47*46/(2*1) = 1081.

See more details here. Note that you use Google to evaluate this by typing in 47 choose 2.

[prowannabie]

where did u get the 46 from?

[BruceZ]

[ QUOTE ]
where did u get the 46 from?

[/ QUOTE ]

Since we are choosing 2, the numerator has 2 terms counting backwards from 47, so it is 47*46. This comes from the fact that C(47,2) = 47!/(47-2)!/2! = 47!/45!/2!, and since 47! = 47*46*45!, the 45! cancels out to give 47*46/2!.

Here are a couple more examples:

C(47,3) = 47*46*45/(3*2*1)

C(52,5) = 52*51*50*49*48/(5*4*3*2*1)