After borrowing 1000, it becomes: 99( 10) (take 10 as a single digit).

The vertical calculation is as follows:

1000-5 can be regarded as (990+10)-5 = 990+(10-5) = 990+5 = 995.

In vertical calculation, 1 is borrowed from the previous digit, and 10 is taken from the last digit. Because our numbers are all decimal, and 10 enters 1, 1 as 10.

Extended data:

1000 subtraction vertical calculation, a unit is borrowed from ten digits to 1, and as 1000, ten digits are borrowed from hundred digits to 1. Because ten digits are borrowed from 1, the ten digits are still 9, and so on.

Subtraction is one of the four operations, and the operation of subtracting one number from another is called subtraction; Given the sum of two addends and one of them, the operation of finding the other addend is called subtraction. The symbol of subtraction is "-",which is pronounced as negative sign.

Subtraction by abdication, a special mathematical term, can also be called subtraction by borrowing. That is, when two numbers are subtracted and the number of digits to be subtracted is not enough, borrowing the previous digit is equivalent to adding 10 to this digit, and then calculating.

Baidu encyclopedia-subtraction

Baidu encyclopedia-abdication subtraction