Question

jim has 8 CDs that he is going to give away. He lets his best friend choose 2 of the 8 CDs. How many different groups of 2 CDs are possible?

Answer 1

3 because if he has 8 and his friend takes 2 that would =6 so 3 groups of 2= 3x2

Answer 2

27

Explanation:

1 with 2,3,4,5,6,7,8=7 pairs

2 with 3,4,5,6,7,8=6 pairs

3 with 4,5,6,7,8=5 pairs

4 with 5,6,7,8=4 pairs

5 with 6,7,8=3 pairs

6 with 7,8=2 pairs

7,8=1 pair

Add them to get 27