The addition of two digits can be regarded as two addition formulas, such as 13+43, which can be regarded as 3+3=6 for single digits and 1+4=5 for tens, where ten digits represent five tens and single digits represent five ones, that is, 13+43=56.
Related content:
The decimal counting method is characterized by "full 10 into one". In other words, every 10 unit forms a higher unit adjacent to it. That is, 10 is called "ten", 10 is called "hundred", 10 is called "thousand" and 10 is called "ten thousand".
One (a), ten, hundred, thousand, ten thousand, one hundred thousand, one million (trillion), ten million, one billion, ten billion, one hundred billion ... are all units of counting.
Numbers mean that when writing numbers, the numbers are arranged side by side in a line, and each number occupies a position. These positions are called numbers. Starting from the right end, the first place is the unit, the second place is the tenth place, the third place is the hundred places, the fourth place is the thousand places, and the fifth place is the ten thousand places, and so on. This shows that the concept of counting unit and number is different.
However, their relationship is very close. "4" means 400 in hundreds, "7" means seven tens in tens, and "5" means five ones in tens.