I have 5 different biology textbooks and 4 different economics textbooks. In how many ways can I place the 9 textbooks on a bookshelf, in a row, if there must be an economics textbook in the middle, and there must be a biology textbook at each end?
+658 I'm not the best at counting and probability problems, so don't get mad if I get this question wrong.
1. There are \(4*P{5 \choose 2}=240\) ways to place an economics text book in the middle as well as place a biology textbook at each end.
2. There are \(6!\) ways to arrange the remaining text books.
So \(720*240=172800\) total ways.
