"tuo shi" means to detach from vertical equations and write out the entire calculation process. the first appearance of "tuo shi" in primary school is in the second unit of the second grade of the jijiao edition mathematics textbook.
for second-grade children, we can explain the meaning of "tuo shi" in the following way: (1) for each operator symbol in the equation, we write an equal sign; (2) the equal sign should be written on the left side of the entire equation, and all equal signs should be aligned; (3) after the first equal sign, write the calculated result of the first two numbers, and then copy the second operator and the number that follows (addition and subtraction without parentheses).
transitioning from one-step calculations to two-step calculations may seem simple, but children find it very difficult to master. the difficulties lie in understanding the meaning of "tuo shi" and the correct writing format, which is as follows:
children are prone to several types of errors, including:
this error occurs when only the two results are written after the equal sign, indicating that the child's understanding is still at the level of one-step calculation and does not understand the meaning of "tuo shi".
this error occurs most frequently, indicating that the child has not moved beyond the memorization pattern of writing the equal sign and result behind the equation taught in the first grade.
this error also occurs frequently because children who have just started with "tuo shi" calculations tend to think that writing an equal sign for each result is necessary. teachers and parents need to emphasize the writing process.