Question

In how many ways 3 mathematics books, 4 history books, 3 chemistry books and 2 Biology books can be arranged on a shelf so that all books of the same subjects are together? ​

Answer 1

Answer:

by grouping

Step-by-step explanation:

by grouping arrange the first mathematics down

later you keep any pad on it

later you keep history book in middle keep another pad on it

later biology book keep in first

Answer 2

First we take books of a particular subject as one unit. Thus there are 4 units which can be arranged in 4! = 24 ways. Now in each of arrangements, mathematics books can be arranged in 3! ways, history books in 4! ways, chemistry books in 3! ways and biology books in 2! ways. Thus the total number of ways = 4! × 3! × 4! × 3! × 2! = 41472.