1 is directly proportional, and the total price divided by quantity = unit price (certain), that is, the proportion must be directly proportional.

2, out of proportion, the proportion and product are not necessarily.

3, in direct proportion, is the same as 1.

4, out of proportion, the number of pages read+the number of pages not read = the total number of pages, and the sum is certain, not the ratio is certain, and the product is certain, so it is out of proportion.