Question

Four different mathematics books, six different physics books, and two 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 mathematics books must stand together

Answer 1

Answer:

a) 207,360 ways

b)8,709,120  ways

Step-by-step explanation:

Total number of subjects= 3

Number of mathematics books = 4

Number of physics books = 6

Number of chemistry books = 2

Part a:

Number of possible arrangement s= 3! 4! 6! 2!= 6*24*720*2= 207360 ways

In this we have included 3! because the books have to be placed in such a manner that the books in each particular subject must all stand together.

Part b:

Similarly the mathematics books must stand together so they are treated as

The total number of books will be

Physics books + Chemistry books+ Mathematics books= 6+2+1(treated as single) = 9

But there are 4 different mathematics books so these can be arranged in 4 ways.

Total number of ways in which these books can be arranged = 9! 4!= 8709120  ways.