Q: There are 5 interesting 1-hour tv shows you'd like to watch: American Idol, Boston Legal, CSI, Dr. Phil, and Extreme Sports. However, you only have 2 hours to watch any combination of 5 tv shows. You don't care which one you see first, but you want to watch 2 different shows. How many combinations of shows can you see?
UNANSWERED.
The correct answer is E.
A: The correct answer is 10.
Since the order does not matter, the formula is # of combinations = # of shows you can watch the first hour * # of shows you can watch the second hour / 2 We can watch any show in the first hour, so there are 5 possibilities there. In the second hour, we've already seen one show, and have 4 shows left that we haven't seen. Since we don't care about order (CSI, then Dr. Phil or Dr.Phil, then CSI is the same), we divide by 2. 5 × 4 / 2 = 10
Another way to get the answer is to list all the possibilities:
