# number of ways a switch can be set

• Nov 22nd 2009, 09:05 AM
renlok
number of ways a switch can be set
Quote:

if 8 switches can set to position a or b and an equal amount of switches are set to a as to b. How many ways could this be done?
i though you could do this with $\frac{8!}{4!.4!}$ but i got the wrong answer.

D: i suck at probability
• Nov 22nd 2009, 09:32 AM
Plato
Quote:

Originally Posted by renlok
i though you could do this with $\frac{8!}{4!.4!}$ but i got the wrong answer.

There are two possiblities for each of eight switches: $2^8.$
• Nov 22nd 2009, 10:23 AM
renlok
yeah but 4 switches have to be a and 4 have to be b
• Nov 22nd 2009, 10:34 AM
Plato
Quote:

Originally Posted by renlok
yeah but 4 switches have to be a and 4 have to be b

Well then it is $\frac{8!}{(4!)^2}.$