Can you talk about what should be paid attention to when adding and subtracting two digits and adding and subtracting 100 digits and 10 digits? What's the connection between them?

Pay attention to the addition and subtraction of single digits and ten digits when adding and subtracting two digits; The oral calculation of adding and subtracting hundreds and tens belongs to the addition and subtraction of three digits, that is, the addition and subtraction of one, ten and hundreds digits;

The relationship between them is that the addition and subtraction of two digits is the only way to add and subtract three digits, and it will be easier to learn to add and subtract three digits if you learn to add and subtract two digits.

The steps of adding and subtracting two digits are as follows:

1, add one digit first and then ten digits. When the single digits add up to ≥ 10, enter 1 in the ten digits.

2. When subtracting, subtract the single digits first. If the subtraction is not enough, borrow 1 from ten digits, and then ten digits.