Editing Preferred number (section)

==Renard numbers==
{{Main|Renard series}}

In 1870 [[Charles Renard]] proposed a set of preferred numbers.<ref name="Sizes_2014"/> His system was adopted in 1952 as international standard [[ISO 3]].<ref name="ISO_3_1973"/> Renard's system divides the interval from 1 to 10 into 5, 10, 20, or 40 steps, leading to the R5, R10, R20 and R40 scales, respectively. The factor between two consecutive numbers in a [[Renard series]] is approximately constant (before rounding), namely the 5th, 10th, 20th, or 40th root of 10 (approximately 1.58, 1.26, 1.12, and 1.06, respectively), which leads to a [[geometric sequence]]. This way, the maximum [[relative error]] is minimized if an arbitrary number is replaced by the nearest Renard number multiplied by the appropriate power of 10.  Example: 1.0, 1.6, 2.5, 4.0, 6.3