If numbers are rounded or truncated then inaccuracies will occur. The size of the inaccuracy may increase if these numbers are used in complex calculations.

Truncation - ignore all information beyond a given number of decimal places (or significant figures).

Example : 5.26 truncated to one decimal place is 5.2

Example : 53,729 truncated to 2 sig.figs is 53,000

Rounding - take the nearest number with the given number of decimal places (or significant figures).

Example : 5.26 rounded to one decimal place is 5.3

Example : 53,729 rounded to 2 sig.figs is 54,000