People prefer to work with round numbers because they are easy to remember and easy to use. For example, most people would rather multiply 4 x 10 rather than 3.5 x 9.5. It is important to know when a round number can be used for convenience. Sometimes the way a number is rounded will affect the accuracy of a computation, introducing a degree of error. If a person is using a blend of exact and rounded numbers in one computation, it may be very difficult to know the accuracy of the answer. There are some basic ground rules for approximation and rounding.

There are actually two forms of approximation: truncation and rounding.

A truncated number is cut off. The truncation is shown by three dots following a series of decimals. All of the digits are valid up to the point of truncation. The truncated value is...