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The following list includes the continued fractions of some constants and is sorted by their representations. Continued fractions with more than 20 known terms have been truncated, with an ellipsis to show that they continue. Rational numbers have two continued fractions; the version in this list is the shorter one.
13 cm = 1.3 dm – body length of a Goliath birdeater; 15 cm = 1.5 dm – approximate size of largest beetle species; 19 cm = 1.9 dm – length of a banana; 26.3 cm = 2.6 dm – length of average male human foot; 29.98 cm = 2.998 dm – distance light in vacuum travels in one nanosecond; 30 cm = 3.0 dm – maximum leg length of a Goliath birdeater
For example, a 10 cm (3.9 in) circular would have a maximum precision approximately equal to a 31.4 cm (12.4 in) ordinary slide rule. Circular slide rules also eliminate "off-scale" calculations, because the scales were designed to "wrap around"; they never have to be reoriented when results are near 1.0—the rule is always on scale.
A football field is often used as a comparative measurement of length when talking about distances that may be hard to comprehend when stated in terms of standard units. An American football field is usually understood to be 100 yards (91 m) long, though it is technically 120 yards (110 m) when including the two 10 yd (9.1 m) long end zones.
More precisely, the order of magnitude of a number can be defined in terms of the common logarithm, usually as the integer part of the logarithm, obtained by truncation. [ contradictory ] For example, the number 4 000 000 has a logarithm (in base 10) of 6.602; its order of magnitude is 6.
Alternatively, the quick approximation 99/70 (≈ 1.41429) for the square root of two was frequently used before the common use of electronic calculators and computers. Despite having a denominator of only 70, it differs from the correct value by less than 1/10,000 (approx. 7.2 × 10 −5). Its simple continued fraction is periodic and given by:
When a real number like .007 is denoted alternatively by 7.0 × 10 —3 then it is said that the number is represented in scientific notation.More generally, to write a number in the form a × 10 b, where 1 <= a < 10 and b is an integer, is to express it in scientific notation, and a is called the significand or the mantissa, and b is its exponent. [3]
It is useful because the number can be copied and pasted into calculators (including a web browser's omnibox) and parsed by the computer as-is (i.e., without the user manually purging the extraneous characters). For example, Wikipedia content can display numbers this way, as in the following examples: 149 597 870 700 metres is 1 astronomical unit