Cross multiplication

Calculator and formulas for calculating the cross multiplication


Cross multiplication is a method of elementary arithmetic to calculate the value of a variable in an equation involving two fractions or rational expressions (Not to be confused with Cross product).

To perform the calculation, enter the values of the varibles, then click the 'Calculate' button.


Cross multiplication

  Input
  Variable a   Variable b
/
=
  Variable c   Result x
/
Decimal places

Formula and example


The formula for the cross multiplication consists of two pairs of values that are related to each other.

\(\displaystyle a/b=c/x\)   or   \(\displaystyle\frac{a}{b}=\frac{c}{x}\)

The formula is changed for the calculation:

\(\displaystyle x=\frac{b ·c}{a}\)

Example


If 4 pears cost 2 euros, how much do 6 pears cost?
\(\displaystyle 4/2=6/x\)   or   \(\displaystyle\frac{4}{2}=\frac{6}{x}\)
\(\displaystyle x=\frac{2 ·6}{4} = 3\)

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