This problem can be solved by interpolation:

Arrange five math books first, with six spaces between them and at both ends.

()c 1() c2() c3() c4() c5()

Insert C < 6,4 > into the physics book * * *; = 15 method,

After inserting the physics book,

There are 1 1 spaces between the two ends and between books.

At this time, three chemistry books were inserted, * * * C < 1 1, 3>；; = 165 methods,

Therefore, * * has 15* 165=2475 methods.