Posted by kitkat on Tuesday, November 16, 2010 at 6:43pm.
combinations of 14 things two at a time = 14!/[12!(2!)]=14*13/2 = 7*13 = 91
but some of those are matching, namely 7 pairs, so there are 91-7 = 84 ways
Why did you divide the answer from 14*13 by 2?
23! = 2*1 = 2
excuse typo
2! = 2*1 = 2
combinations is
n!/[ (n-r)! r! ]
here n=14
r = 2
14! = 14*13*12 * 11 etc
12! =12*11 etc
so
14!/12! = 14 * 13
now divide that by 2! which is 2
what I did is
Total= 14*13=182
Matched pairs=7*2=14
182-14- 168 possibilities
but you can not tell left-right
from
right-left
well for the matched pairs part the 7 is the pairs and the 2 is the orders of pairs LR and RL
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