help with ncr and npr (1 Viewer)

[viva]

can someone tel me the difference??
i always get heaps confused.
thanks

 

[honky tonk]

I know I should probably know this, but what exactly do ncr and npr stand for?

 

[snobby airlines]

nPr = ordered selections, this is for like a car registration number plate (P= Permutations)

nCr = unordered selections, eg selecting a soccer team out of 15 peeps. (C= combinations)

 

[honky tonk]

Permutations? Combinations? Discombobulations?

I have absolutely no idea what you're talking about.

I was confident before reading that post!

 

[viva]

thanks. now at least i know ill get one mark out of a hundred

 

[kimmeh]

since when was permutations and combinations in general maths?
its not in 2 unit.. i dont think..

 

[freaking_out]

Originally posted by kimmeh
since when was permutations and combinations in general maths?
its not in 2 unit.. i dont think..

yeah was this a joke to mock the general students?

 

[arls]

ordered selections = n x (n-1) x (n-2) x (n-3) x . . . for example if there are five friends... and you have to put them in places how many places could they sit?
5x4x3x2x1 = whatever the answer is.

unordered selections... where order does not matter :

= the top line is the number of objects ... only the right amount to fill up the available spaces! divided by the number of available places decreasing and timsing to zero.

eg. three students are selected out of 8 students to represent the school at a festival. how many combinations of 3 students are possible? (note order does NOT matter here.)

no of arrangements of 3 students from 8 divide by no of ways 3 students can rearrange themselves.
8x7x6 divide by 3x2x1 = calculate!

its a bit confusing hope ive made some sense.. i also hope you ppl see this b4 the exam... unlikely but it helped me revise at least!!