keep-flip-change

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

$$\frac{a}{b}÷\frac{c}{d}$$

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

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

Title	keep-flip-change
Canonical name	Keepflipchange
Date of creation	2013-03-22 15:59:52
Last modified on	2013-03-22 15:59:52
Owner	Wkbj79 (1863)
Last modified by	Wkbj79 (1863)
Numerical id	4
Author	Wkbj79 (1863)
Entry type	Definition
Classification	msc 97D40
Synonym	KFC
Synonym	K.F.C.