Calculate the formula according to the meaning of the question:

1440÷ 10÷6

= 144÷6

=(24x6)÷6

=24

So there are 24 books on each floor on average.

The nature of division calculation:

The difference between two numbers is divided by a number, and the quotient obtained by dividing the minuend by this number can be subtracted from the quotient obtained by dividing the minuend by this number. Example: (65-39) ÷13 = 65 ÷13-39 ÷13 = 2.

Dividing by two divisors in succession is equal to dividing by the product of these two divisors. Sometimes simple operations can be performed according to the nature of the division. For example: 300 ÷ 25 ÷ 4 = 300 ÷ (25× 4) = 300 ÷100 = 3.