+190 I have $3$ different mathematics textbooks, $2$ different psychology textbooks, and $2$ different chemistry textbooks. In how many ways can I place the $7$ textbooks on a bookshelf, in a row, if all three mathematics textbooks must be together?
+37128 Oopps...I didn't read the entire question ...
the three math books together can be arranged in 6 ways ( 3! or 3 P3)
then they act as one object of 5 objects 5 P 5 = 120 ways to arrange the books ( 5!)
Then 6 x 120 = 720 ways
