SOLUTION: Please please please help. Due tonight. I have done all of the others, but cannot get this one. How many committees can be formed from a group of 9 doctors of each committee con

Question 354257: Please please please help. Due tonight. I have done all of the others, but cannot get this one.
How many committees can be formed from a group of 9 doctors of each committee consists of 7 doctors. I must also explain how I ca,e to this conclusion.
Thank-you so much n advance.
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
each committee leaves out 2 of the 9 doctors

there are 9 ways to leave out one doctor

for each of those 9 ways , there are 8 ways to leave out the second doctor
___ so 72 ways
___ BUT ... leaving out Dr. Smith and then Dr. Jones , is the SAME as leaving out Dr. Jones and then Dr. Smith

so the possible committees is 72/2