Definitions: In an approximate number the leftmost digit is said to be the most significant digit and the rightmost digit is the least significant digit. All the digits in the number are significant digits (also known as significant figures or sig. figs.) with one exception: if the digit is a zero that is used just to locate the decimal point then it is not significant. The accuracy of an approximate number is given by the number of significant digits in it. The precision of an approximate number is given by the position of the rightmost significant digit. |
Rounding: When rounding to a certain place value then all digits to the right of that place are dropped. If the first dropped digit is 0, 1, 2, 3, or 4 then the least significant digit kept is not changed. (This is called rounding down.) If the first dropped digit is 5, 6, 7, 8 or 9 then the least significant digit kept is increased by 1. (This is called rounding up.) |
the rounding the rule used 4.384 → 4.38 first dropped digit is a 4 so round down 4.3851 → 4.39 first dropped digit is a 5 so round up 0.00043851 → 0.00 first dropped digit is a 0 so round down
the rounding the rule used 4.384 → 4.38 first dropped digit is a 4 so round down 43851 → 43900 first dropped digit is a 5 so round up 0.00043851 → 0.000439 first dropped digit is a 5 so round up
Algebra Coach Exercises |