What is an estimate? The so-called estimate is a rough calculation. There are three kinds of estimates: one is to calculate the maximum value, the other is to calculate the minimum value, and the third is to calculate the approximate amount. How to estimate? In the estimation, we should first approximate the numerical values involved in the calculation, and turn the more complicated calculation into a simple one that can be calculated by mouth, and get an approximate value, such as: the estimation is 32×58, and the maximum value: all are calculated by integers ten digits larger than the original value, and the maximum value is 40× 60 = 2400; Minimum value: all are calculated by integers less than the original value, and the minimum value is 30× 50 =1500; What is approximately equal to: use the "rounding method" to calculate the approximate number, which is about 30× 60 = 1800.

2. Is estimation easier than accurate calculation?

Some people think that estimation is to turn complex calculation into simple oral calculation, so estimation is much easier than pen calculation. Is estimation really easier than accurate calculation? We might as well analyze it from the following two aspects:

⑴ Thinking process: All written calculations have their complicated calculation principles. When students learn written calculation, they first carry out complex thinking analysis and logical reasoning, and then compare, analyze and summarize the calculation process to get the calculation rules. Complex thinking activities in the process of calculation are the calculation principles and the basis of calculation. Calculation rules are stylized operation methods that simplify complex thinking activities and calculate according to certain procedures. So we don't think about every step of calculation in the process of writing, which greatly reduces the difficulty and intensity of thinking. As long as you have some training, you can reach the level of correct and fast calculation, so there is no complicated thinking activity in the writing process. Probably not the same. All thinking processes cannot be simplified. Be sure to think about reasoning step by step, for example, estimate 32×58, first think: 32 is close to dozens, remember 30, then think: 58 is close to dozens, remember 60, and then extract the first memory information 30. Think again: 3× 6 = 18, there are two zeros at the end of 30 and 60, so adding two zeros after 18 will get 1800. Since 30 is less than 32 and 60 is greater than 58, 1800 is neither the maximum nor the minimum, and the number should be in. Judging from the intensity of thinking, estimation has to go through a series of thinking activities such as thinking many times, remembering many times, extracting information, calculating, comparing and judging, so estimation is more difficult than writing.

⑵ Working memory: Working memory belongs to short-term memory and is the perception of a short moment. Psychological research shows that adults can only remember about 5~9 independent information units, and children's working memory information is even less. The result of vertical calculation is that as long as you remember "how much to enter", "how much to retreat 1" and "how much to add" in your mind, there is only one or two pieces of information in your working memory, so there is little information in your working memory during calculation. But the estimation is different: first, we must think about the approximate number of each number, remember the approximate number, extract the relevant information in memory, and then calculate, so the amount of information we remember in our minds is much more than that of vertical calculation, even exceeding the memory ability of primary school students, so the estimation is more difficult than writing.