Cross-multiplication

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In mathematics, specifically in elementary arithmetic and elementary algebra, given an equation between two fractions or rational expressions, one can cross-multiply to simplify the equation or determine the value of a variable. The method is also occasionally known as the "cross your heart" method because lines resembling a heart outline can be drawn to remember which things to multiply together. Given an equation like a b = c d , {\displaystyle {\frac {a}{b}}={\frac {c}{d}},} where b and d are not zero, one can cross-multiply to get a d = b c or a = b c d . {\displaystyle...

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