## anonymous one year ago Find the number of ways to listen to 4 different CDs from a selection of 15 CDs?

1. ganeshie8

You can choose $$4$$ CDs from a collection of $$15$$ CDs in $$\binom{15}{4}$$ ways. Each of these groups of $$4$$ CDs can be listened in $$4!$$ ways, so the total number of ways to listen $$4$$ CDs from a collection of $$15$$ CDs is $$\binom{15}{4}*4!$$

2. ganeshie8

Alternatively, you can see that there are $$15$$ choices for the first CD. After that, there are $$14$$ choices for the second CD. After that, there are $$13$$ choices for the third CD. After that, there are $$12$$ choices for the fourth CD. So, the total number of ways to listen to $$4$$ CDs from a collection of $$15$$ CDs is simply $15\times 14\times 13\times 12$

3. anonymous

32,760?

4. anonymous

thank you

5. ganeshie8

Looks good!

6. UsukiDoll

correct 15 x 14 x 13 x 12 = 32,760