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July 24, 2014

July 24, 2014

Posted by **Emily** on Wednesday, February 17, 2010 at 10:00pm.

- Data management -
**Secret**, Thursday, April 11, 2013 at 7:35pmLet's say Bob is in both clubs. There are 11 other people.

Two cases: Bob is on the committee, or not:

a) Bob included:

First choose him, then choose any 3 of the other 11, since both clubs are represented by Bob:

11C3 ways to do that.

b) Bob excluded:

Now start with 11C4 (committees made up of the other 11 people).

Subtract 4C4 = 1 way with all 4 others from the camera club,

and 7C4 = 35 ways with 4 others from the math club.

11C3 + 11C4 - 1 - 7C4 = 165 + 330 - 1 - 35 = 459

Or we could say:

there are 12C4 total committees ( = 495 = 165 + 300 )

not worrying about Bob, and then just subtract the 1 which is the 4 camera club members

who are not Bob and the 35, which is the same for the math club.

- Data management -
**Secret**, Thursday, April 11, 2013 at 7:35pmLet's say Bob is in both clubs. There are 11 other people.

Two cases: Bob is on the committee, or not:

a) Bob included:

First choose him, then choose any 3 of the other 11, since both clubs are represented by Bob:

11C3 ways to do that.

b) Bob excluded:

Now start with 11C4 (committees made up of the other 11 people).

Subtract 4C4 = 1 way with all 4 others from the camera club,

and 7C4 = 35 ways with 4 others from the math club.

11C3 + 11C4 - 1 - 7C4 = 165 + 330 - 1 - 35 = 459

Or we could say:

there are 12C4 total committees ( = 495 = 165 + 300 )

not worrying about Bob, and then just subtract the 1 which is the 4 camera club members

who are not Bob and the 35, which is the same for the math club.

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