Proportion. Basic property of proportion

A proportion is an equality of two ratios:

\frac{a}{b}=\frac{c}{d}

(or colon notation). Fundamental property of a proportion: the product of the extremes equals the product of the means:

a\cdot d = b\cdot c

. With this rule you can find an unknown term.

For

\frac{a}{b}=\frac{c}{d}

: extremes are

a,d

; means are

b,c

Cross products are a quick check for equivalent ratios

Solve for the unknown from the equality of products

Proportion explained

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