Addition and subtraction align the decimal points of two numbers, and then calculate according to the ordinary addition and subtraction algorithm. Finally, the decimal point of the result is the same as the original number. For example: 3. 14+2.56 = 5.70, 2.98- 1.69 = 1.29.

Multiplication removes decimal points from two numbers, then multiplies them by integers, and adds decimal points between the second and third digits from right to left in the final result. For example: 2.5× 1.3 = 3.25.