"Direct thinking" is the most commonly used way of thinking to solve problems. Generally, the solution to the problem is directly found through analysis, synthesis and induction.

Second, the idea of reduction.

According to the known conditions, backward reasoning step by step until the problem is solved, which is called reductive thinking. To solve this kind of problem, we can count back from the final result, original addition and subtraction, original subtraction and addition, original multiplication and division, and original division and multiplication.

Third, hypothetical thinking.

I asked many primary and middle school students in the online open class. If you can't do a math problem, what will you do? Many students answered to give up. In fact, at this time, you might as well try your hypothesis. When solving mathematical problems, we can't do without hypothetical thinking, especially when solving complex problems. If we can think with "hypothetical" thinking, it is often simpler and more convenient than other thinking. Let's make a hypothesis first and then prove it step by step.