99 divided by 20 equals 4, leaving 19.
When checking, first calculate 20 times 4, and the vertical expression is as follows:
Then calculate 80+ 19, and the vertical expression is as follows:
After the result of the topic is calculated, it is calculated once by inverse operation (such as addition for subtraction and multiplication for division) to check whether the result of the previous operation is correct.
Check calculation of extended data division
According to the division formula: dividend ÷ divisor = quotient?
(1) Multiply the calculated quotient by the divisor to check whether the result is equal to the dividend.
(2) Divide the dividend by the calculated quotient and check whether the result is equal to the divisor.
For example, check calculation: 8÷2=4.
(1)4X2=8, which proves that the result is correct.
(2)8÷4=2, which proves that the result is correct.