Addition (usually signified by the plus symbol +) is one of the four basic operations of arithmetic, the other three being subtraction, multiplication and division. The addition of two whole numbers results in the total amount or sum of those values combined.
The percentage of completion method is a revenue recognition accounting concept that evaluates how to realize revenue periodically over a long-term project or contract. Revenue, expenses, and gross profit are recognized each period based on the percentage of work completed or costs incurred.