Image (left)
The ratio (diagonal/side) for a regular pentagon is called the golden number, which is 1.618 . . . Its exact value is (51/2+1)/2.

(below)
Many people believe that the golden rectangle, the ratio of whose sides is the golden number, is the most eye-pleasing rectangular shape.


Image

Ratios

When two (or more) numbers are compared by division, the comparison is called a ratio. In other words, a ratio is a method of comparing two or more numbers or variables. Ratios are generally written as:
Ratio Image

The ratio "a:b" is read "a is to b." The number that comes after the "to" goes second or at the bottom of the fraction.

The ratio of 4 to 12 is 4/12 or 1/3. When the ratio is expressed as a fraction, it is usually reduced to the lowest term.

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