Question 737642: 4 different math books, 6 different physics books and 2 different chemistry books are to be arranged on a shelf. How many different arrangements are possible if
a) The books in each particular subject must all stand together
b) Only the math books must stand together
Answer by Susan-math(40)   (Show Source):
You can put this solution on YOUR website! 1) First choose the order of the books subjects: 3 subjects so 3! Then arrange each subject: 4!6!2! So all together: 3!4!6!2!=207,360
2) First arrange the math books. there are 4! ways to do this. since they have to stay this way - together - consider the math subject now as 1 big "book", 6 physics boos and 2 chemistry books.
Then we have 1+6+2=9 "books" and can arrange them 9! ways.
So we can have 4!9!=8,709,120 arrangements.
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