Application problem is the most important thing in mathematics teaching. When redundant conditions appear in application problems, many students are often affected by redundant conditions, and the method of solving problems is cumbersome or even wrong. Then, how to teach application problems with redundant conditions? 1. Types of redundancy conditions for application questions 1. The type of absolute redundancy is as follows: "The school bought 1500 books and lent them to 18 classes, with 50 books in each class. How many books did the school borrow? " The known condition of "1500 books" in the problem is useless when solving problems, no matter from which angle students think. This redundancy condition is usually called absolute redundancy condition. This kind of application questions focus on students' ability to examine questions, and generally do not appear in basic exercises, but often appear in review and consolidation. 2. Necessary redundancy: "A factory has two standard workshops, one is 15 workshop and the other is 12 workshop. How many workshops are there in this factory? " On the surface, the condition of "two standard workshops" in the title seems redundant to the question of "how many workshops are there in this factory". However, if the known condition of "two standard workshops" is removed, the title will be incomplete, because after removing the condition of "two standard workshops", it is not clear how many workshops there are in this factory. Therefore, the condition of "two standard factories" cannot be removed and is not used in the calculation. We call this redundancy condition necessary redundancy condition. This necessary and sufficient condition and redundant condition are confusing for students to solve problems. ....