1 to 10

First of all, there should be 10 * 10 = 100 kinds of addition formulas composed of two numbers.

However, since similar addition formulas such as 1+2 and 2+ 1 should be regarded as the same, the actual situation should be less than 100.

You can think of the above as taking two numbers from 1 to 10 at will, and then consider the case of 1+ 1.2+2, then the actual situation is that C (2, 10) = plus 1+ 65 exists.

the second part

1 1 to 20

There will be no repetition at this time, and there can be 10 * 10 = 100 kinds of addition formulas.

To sum up, there are 155 addition formulas.