a student is given a reading list of ten books from which he must select two for an outside reading requirement, how many ways can he choose?
- -j.Lv 75 months ago
He has to choose two books.
His first choice can be any one of the 10 books.
Whichever book he chooses first, the second choice will be one of the 9 remaining books.
So there are 10 first choices, and 9 second choices for every first choice. That means the total number of ways he can choose is 10 * 9, or 90.
Hope that helps :)