one of the few places that multiples of 10 exist in U.S. customary units is obscure units of area:
10 square chain = acre
10 acre = square furlong
however, this feels awkward because 10 congruent squares cannot be arranged into a larger square. it would have been nice if our counting system were based on a square number.
acre is a square with side length sqrt(10) ~= 3.162277660168379332 chain, or 0.3162277660168379332 furlong.
compare this with the metric system which does area in powers of 100: square meter, are, hectare, square kilometer, (megaare? megare?), (hectomegaare?), square megameter. (but previously on sqrt(10) elsewhere in the metric system.)
64 square furlong in a square mile, realizable as an 8x8 array of square furlongs. 100 square chain in a square furlong.
partition a square into 10 congruent pieces. 10 strips, or a 2x5 array of rectangles, work. are there any other ways?
an acre is a strip 1 chain by 10 chain (22 yard by 220 yard).
(a football field is (53 + 1/3) yard wide, or (2 + 14/33) chain. including end zones, it has area (1 + 117/363) = (1 + 39/121) acre. excluding end zones, (1 + 37/363) acre.)
partition a square into 10 regions of equal area, optimizing for compactness of the regions by some measure.
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