the A format

An optimization's problem : what is the best shape for a sheet of paper ?
To avoid scraps during cuttings in order to obtain smaller sheets, the most simple is to chose a rectangle such as, if it is cut into two, we get two identical rectangles similar to the first one (preservation of the sides' ratio).
For the starting sheet - format A0 - it is natural to choose a rectangle of area 1 m².

format A An formats

The size of the A4 format is the quarter of that of the A0 format: 29.7 cm by 21 cm (rounded values),
and it's area is 1/16 m² = 625 cm².

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updated 11-10-2001