In a class of 9 students everyone gets along well, except for Martha that keeps arguing with Peter and Mark. A comittee of 5 students will be formed and it requires no fights. How many comittees can be formed?

a) 83
b) 80
c) 75
d) 71

I've tried everything but I cant get at any options. Help?

Question

In a class of 9 students everyone gets along well, except for Martha that keeps arguing with Peter and Mark. A comittee of 5 students will be formed and it requires no fights. How many comittees can be formed?

a) 83
b) 80
c) 75
d) 71

I've tried everything but I cant get at any options. Help?

anonymous · Answer

well can be assume the martha can't be on the committee?

bahrom7893 · Answer

No.. hold on..

bahrom7893 · Answer

If it was just a committe of 5 students it would have been 9C5

bahrom7893 · Answer

suppose none are picked in the group.. that means we have 9-3 = 6 students, and we gotta pick 5, so 6C5

anonymous · Answer

83

bahrom7893 · Answer

That's one option. Suppose Martha gets picked, but that means neither Peter nor Mark can be picked, so:
7C5
Peter gets picked -> Martha, Mark can't be on the committee
7C5
Mark gets picked ->M and P can't be on the committee:
7C5 again.

bahrom7893 · Answer

by the way im not sure of the solution.. atjar how did u get ur answer?

anonymous · Answer

8C5+6C5+7C5

bahrom7893 · Answer

can u explain the reasoning behind that? sorry but im taking probability too.. I was trying to multiply these out... ohh yea.. OR.. so you add.

anonymous · Answer

1st is for excluding Martha.
2nd is for excluding all three
3rd for excluding Peter and Mark

bahrom7893 · Answer

OHHHH YES I SEE.. I'm dumb.. I assumed Peter and Mark would argue with each other too.. omg... Melinda, can u post another one of these?

anonymous · Answer

haha what do you mean another one? hmmm ok just wait a sec then! and thanks a lot you both

bahrom7893 · Answer

another one of these questions.

bahrom7893 · Answer

actually do u wanna study for this somewhere Melinda? Skype or something.. I'm also trying to study for my probability exam right now.

bahrom7893 · Answer

gotta go through three chapters.. hate studying on my own lol

anonymous · Answer

well right now i cant, im using my uncles laptop and i have no mic to skype :/ btw my exam is coming, too... im freaking worried

bahrom7893 · Answer

no i dont need the cam, i just need some chat.. dang it i should've formed a group called probability..

anonymous · Answer

haha you should've. ok let me see if i can log in