Editing Preferred number (section)

=={{anchor|1-2-5 series}} 1–2–5 series==
In applications for which the R5 series provides a too fine graduation, the 1–2–5 series
is sometimes used as a cruder alternative. It is effectively an E3 series rounded to one significant digit:

:… 0.1 0.2 0.5 1 2 5 10 20 50 100 200 500 1000 …

This series covers a [[decade (log scale)|decade]] (1:10 ratio) in three steps. Adjacent values differ by factors 2 or 2.5. Unlike the Renard series, the 1–2–5 series has not been formally adopted as an [[international standard]]. However, the Renard series R10 can be used to extend the 1–2–5 series to a finer graduation.

This series is used to define the scales for graphs and for instruments that display in a two-dimensional form with a graticule, such as [[oscilloscope#Graticule|oscilloscopes]].

The [[denomination (currency)|denominations]] of most modern [[Currency|currencies]], notably the [[euro]] and [[Pound sterling|sterling]], follow a 1–2–5 series. The United States and Canada follow the approximate 1–2–5 series 1, 5, 10, 25, 50 (cents), $1, $2, $5, $10, $20, $50, $100. The {{1/4}}–{{1/2}}–1 series (... 0.1 0.25 0.5 1 2.5 5 10 ...) is also used by currencies derived from the former [[Dutch gulden]] ([[Aruban florin]], [[Netherlands Antillean gulden]], [[Surinamese dollar]]), some Middle Eastern currencies ([[Iraqi dinar|Iraqi]] and [[Jordanian dinar|Jordanian]] dinars, [[Lebanese pound]], [[Syrian pound]]), and the [[Seychellois rupee]]. However, newer notes introduced in Lebanon and Syria due to inflation follow the standard 1–2–5 series instead.