Who knows how to calculate quickly with your fingers? How can you not tutor your children? For example, 1+4 3+2
You can only learn by yourself before tutoring your children. First of all, I need to know the fast finger calculation formula on my back. 1+4 should be: direct addition is not enough, 50% off for stretching and 50% off for stretching 1. 3+2 is 2 stretching, 5 bending and 3. As long as parents understand the method and then follow the formula, it is indeed simpler than our childhood algorithm, and the result is clear at a glance.