A ratio compares two or more quantities of the same kind. Written as a:b or a/b. Ratios are used in recipes (3:1 flour to water), maps (1:50,000), financial analysis (P/E ratio), and mixing (2-stroke fuel). A proportion is an equation stating two ratios are equal.
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Pro Tip
Cross multiplication solves proportions: if 3/4 = x/12, then 3×12 = 4×x → x = 36/4 = 9. Also useful for unit conversion: x miles / y km = 1 mile / 1.609 km → solve for x.
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Did You Know?
The aspect ratio 16:9 used by modern TVs and monitors was chosen by researcher Kerns Powers in 1984 as the geometric mean of four earlier standards (4:3, 2.39:1 cinema, etc.) — it fits all formats with minimum black bars.
References
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