The point of explanation is that the first step has ten numbers, and there are exactly ten spaces. In general, it is not allowed to reuse any number;

Then let the children observe the formula and realize that this problem has a carry;

Then the formula is decomposed, which can be regarded as two addition problems without carry and one addition problem with carry.

In this way, the ten numbers of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 can be changed into nine numbers of 2, 3, 4, 5, 6, 7, 8, 9, 10, and then the three required addition problems are combined to make the sum/kloc.