Question

**3. Mary is moving and wants photos to
remember her six friends. If pictures are taken so
there is a shot of every possible pair of friends -
including Mary, how many pictures will be taken?
Would one roll of 24 exposures be enough?​

Answer 1

Need pictures of 6 friends & there’s a picture of pair of friends

6 C 2

6! / 2! (6-2)!
15