Answer:
a) 207,360 ways
b)8,709,120 ways
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.