Sort out five different chemistry books first, and there will be P5 5 = 5! Seed arrangement method

Then insert four different physics books in the four gaps between the five books. There are four ways.

Then insert 3 different math books into 8 gaps of 9 books, and select 3 positions from 8 positions first. Is there a C8 3 method? Then the whole array, that is, the methods of C8 3*P3 3 (that is, P8 3), and the three methods are added together, which is about 480. I don't know, right?

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