Two ratios can be equal {proportion} {analogy, mathematics}: a/b = c/d. In proportion, variable can be in numerator and another variable can be in other numerator {direct variation} {direct proportion}: x/3 = y/4. In proportions, product of two variables can be in numerator {inverse variation} {inverse proportion}: x*y = 4. Direct or inverse proportion can have a constant {proportionality constant}: c * (x/3) = y/4 or c * (x*y) = 4.
Proportions can change to product equalities by multiplying {cross-multiply} both equation sides by denominator product: x/3 = y/4 goes to 12 * x/3 = 12 * y/4 = 4*x = 3*y.
Mathematical Sciences>Algebra>Equation>Kinds
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Date Modified: 2022.0224