Posted by **Chelsea P** on Monday, January 28, 2013 at 12:22am.

the student wants to buy 3 CDs, but assume that there are 3 CDs featuring the piano, 5 CDs featuring the trumpet, and 7 CDs featuring the saxophone. (2) In how many ways can the selection be made if CD's featuring at least 2 different instruments are selected?

- Finite -
**Moo**, Monday, January 28, 2013 at 12:44am
There are several ways you can do it, but this way is probably the easiest.

Try selecting 3 CDs from the entire set of CDs, ignoring the other parts of the problem for now. You have 15C3=455 ways.

Then find how many ways they can be chosen so that all three are the same. 3C3+5C3+7C3=46.

Subtract! 455-46 should be your answer, since there's always two different types of instruments!

This is called COMPLEMENTARY COUNTING, and it means that you are counting all possibilities then subtracting the ones you don't want. It's often much easier that way.

- Finite -
**Anonymous**, Monday, February 1, 2016 at 12:30am
idk

## Answer This Question

## Related Questions

- College Finite - A student wants to buy 3 CDs, but assume that there are 3 CDs ...
- Finite: College Math - A student wants to buy 3 CDs, but assume that there are 6...
- MATH - A student who wants to buy 3 CDs, but assume that there are 6 CDs ...
- finite MAth - dent who wants to buy 3 CDs, but assume that there are 4 CDs ...
- Math - Tell whose CD collection has the greater ratio of rock CDs to total CDs. ...
- Math - You have $60.00 in your wallet and want to buy some new CDs. If the CDs ...
- algebra - you buy a storage rack that holds 40 cds. you have 27 cds. write an ...
- math - Julia works at a music store. One of her jobs is to stock new CDs on the ...
- elementary - nuber sense minnie has 6 county cds and 5 rock cds.amanda has 5 ...
- Math - Find the number of each kind of object in the collection Miranda has 24 ...

More Related Questions