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This is a question about work efficiency. You can set this work as 1, then the work efficiency of Party A is 1/a, and that of Party B is 1/b, so the total work efficiency of both parties is 1/a+ 1/b, and the time required for cooperation is equal to work/.

In my opinion, math problems should be done more, and different problems should be chosen for the same type of problems. The so-called practice makes perfect. That's it.

But I think, for this kind of similar application problem, we must read the problem several times before we can figure out the amount of problem solving. Take the question you asked as an example. First of all, you need to know what this question is and the time required for Party A and Party B to cooperate to complete it. Then you might as well put the question aside and think about what you need to know to ask for this quantity. Working time = workload/work efficiency, I think this formula must be taught by your teacher, so mastering the mathematical formula is a key to solving the problem! Going back to the original question, knowing this formula, and then looking at the question, what we know now is the time for Party A and Party B to complete the workload alone, so what can we do to link the conditions given in the question with the formula? This is the problem we will solve next. Look carefully at the topics "A job" and "Finish (a job)". The topic never tells us exactly how much this work (quantity) is, so we can set this work as a certain quantity by hypothetical methods, for example, let the total workload be X (I set it as 1, because this work can be regarded as a whole, even if it is set to be replaced by other letters, it can be arranged in the end. Then we can know the respective work efficiency of Party A and Party B, the individual work efficiency and the total work efficiency. If the known quantity is substituted into the formula "working time = workload/working efficiency", will the problem be solved?