1, what is "complement"?

When two numbers are added, if their sum can just reach integer 10, integer 100, integer 1000, integer 1000, one of them is called the "complement" of the other. For example,1+9 =10,3+7 =10,2+8 =10,4+6 =10,5+5 =10.

In the above formula, 1 is called the "complement" of 9; 89 is called the "complement" of 1 1, and1is also called the "complement" of 89. In other words, two numbers are mutually "complement".

2. Add the complement first.

For example, 36+87+64,99+136+10, 136 1+972+639+28.

Let's try to solve a problem. The formula = (36+64)+87 =100+87 =187. In this way, several numbers that are "complements" to each other are added first, and then subtracted from the minuend, or the number with the same mantissa as the minuend is subtracted first. You can also use "complement" to make numbers close to integer ten, integer hundred, integer thousand and so on. Integers first, then calculate them (pay attention to subtract the added number and add the subtracted number).

3. What is the number of folds?

Numbers such as 22, 666 and 33333 with the same digit are called "overlapping numbers". Mathematical "overlap number" and "overlap number" are different.