Generally speaking, from senior one to senior three, add, subtract, multiply and divide or even add and subtract within 20; Intra-table multiplication; Two digits within 100 can be added or subtracted in decimal; A simple addition and subtraction two-step calculation problem that will not abdicate within ten thousand years; Simple one-digit times two-digit number; Simple decimal addition requires skilled verbal calculation.
After the fourth grade, the content of oral calculation will gradually increase, not only to consolidate the past content, like addition and subtraction of denominator and simple addition and subtraction of different denominator, but also to remember some data on the basis of understanding, such as: 25× 4, 125× 8, 10 to 19 square, etc. For all those who can apply arithmetic and properties to oral calculation.
Secondly, we should train more short-term memory. A calculation problem often involves multi-step calculation, and the intermediate number needs short-term memory. Because of impatience, hurry and fear of trouble, some of the stored information disappears or is temporarily interrupted, resulting in "memory errors and omissions".
For example, in the successive abdication subtraction, 1 is forgotten, which leads to errors in the calculation results, such as 4020- 199, which students can easily calculate as 4020- 199 = 393 1, which is completely related to the storage and memory of intermediate numbers.
There are three kinds of bad mentality of primary school students in the calculation process:
One is to despise psychology, thinking that the calculation problem is a "dead problem", without thinking, ignoring the mistakes caused by the analysis of the calculation problem and the inspection after calculation.
The second is fear of difficulties. It is considered that the calculation problem is boring. Whenever you see a calculation problem with many calculation steps or large numbers, you will feel afraid of difficulties and bored, lacking perseverance, patience and confidence, which greatly reduces the accuracy of calculation.
The third is laziness and disgust. Too lazy to write, unwilling to write one more word, disgusted with calculation, regardless of the size of the number, proficiency or not, all oral calculation, unwilling to write calculus, too lazy to draft, and even no special draft book, calculus book. Often omit necessary steps, skip steps, and fantasize about quick and direct results, thus making mistakes.