Question

There are 3 maths , 4 physics and 5 chemistry books. In how many ways can they be arranged on a shelf so as to keep all the books of the same subject together.

Answer 1

Answer:

Step-by-step explanation:

well,first we have to use the string method

which is nothing but taking all similar books as a single object

so we take 3 maths books as one object,similarly the 4 physics books as one and the 5 chemistry books as one.

so now we have 3 objects.

so now,these three objects can be arranged in 3! ways right.(1)

now,in the first object,the three maths books can be arranged in 3! ways(2),the second object,that is, the 4 physics books can be arranged in 4! ways(3),and the third object,which is the 5 chemistry books which can be arranged in 5! ways.(4)

so finally,the total number of arrangements is= 3!×3!×4!×5!=6×6×24×120= 103680 ways

hope this helps you

thanks