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Assuming you want the numbers to be "nice", i.e. not too large or too small, you could use either millimeters or centimeters. A US nickel is 21.2 mm in diameter* which can also be expressed as 2.12 cm. Of course simply moving the decimal point gives you 21,200 micrometers or 0.0000212 km or ... , but those aren't such convenient representations. (*) rather than "width", because it's circular (责任编辑:) |
