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# keep-flip-change

Let $a,b,c,d\in\mathbb{Z}-\{0\}$. A mnemonic device for calculating

$\frac{a}{b}\div\frac{c}{d}$ |

is KFC. This stands for ”keep-flip-change”. This means that you keep the first fraction as it is, flip the second fraction, and change the problem to a multiplication problem. Thus, the expression above becomes

$\frac{a}{b}\cdot\frac{d}{c}.$ |

This yields that

$\frac{a}{b}\div\frac{c}{d}=\frac{a}{b}\cdot\frac{d}{c}=\frac{ad}{bc}.$ |

Synonym:

KFC, K.F.C.

Type of Math Object:

Definition

Major Section:

Reference

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new image: plot W(t) = P(waiting time <= t) by robert_dodier