Based on counting in tens but it has no symbol for zero and it does not use the idea of place value. It is irrational. It is the positive real number that when squared produces 2. 4. It is the length of the hypotenuse in a right triangle in which both legs are 1 unit in length. Rounding Rounding involves approximation - precision and accuracy.
Precision refers to the number of digits displayed in the representation.
Accuracy measures the error in an approximation. The goal of rounding is to achieve a specified precision and accuracy in an approximation of a number. The goal of approximation is to produce a finite decimal of a required precision or a specified number of significant digits. If the last significant digit is a digit from 1 to 4, you round down. For example 3.124 rounded to 3 significant digits is 3.12.