1, the total number of pages in this novel is unchanged, and the number of pages read before meals accounts for the total; After dinner, she read eight more pages, and the number of pages that have been read accounts for the total; (Page) A: This novel has 448 pages. Comments set the invariant as "1", and take static braking as the breakthrough to solve the problem, which can easily solve the problem. Generally, there are three invariants: 1. When determining the total amount as an invariant, it is usually necessary to specify the specific amount or find out how many parts of the total amount are before and after the specific amount, and calculate the total amount according to its changes. 2. When determining the quantity of one part as invariant, it is usually necessary to make clear that the specific quantity of the other part (or all) is equivalent to a fraction (or several times) of the unit "1", and calculate the unit "1" according to the variation. 3. When determining that the difference of some quantities is invariant, it is usually necessary to sort out the scores (or multiples) of this difference before and after some specific quantities and find a business trip. The invariant of this kind of problem is taken as the unit "1", but it should be noted that the problem is not necessarily the unit "1", so it should be carefully analyzed and calculated flexibly.