Discussion
In Daya’s bag there are 3 books of History, 4 books of Science and 2 books of Maths. In how many ways can Daya arrange the books so that all the books of same subject are together?
Answer: D
Treat each subject as a single block, then arrange within each block.
\[ \text{blocks among themselves} = 3! = 6 \]
\[ \text{History} = 3! = 6, \quad \text{Science} = 4! = 24, \quad \text{Maths} = 2! = 2 \]
\[ 6 \times 6 \times 24 \times 2 = 1728 \]
Forgetting the \( 3! \) for the blocks themselves would give 288; the subjects can appear in any order on the shelf.
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