Question 839331
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Hi,
You have 2 science books, 3 language books, and 4 philosophy books. 
In how many ways can they be arranged on the shelf 
if all books of the same subject are to be together? 

The idea is: if books of same subject are to be together...
Then... how many ways can 3 'units' to be arranged: {{{highlight( 3!)}}}