Algebrarules.com

The most useful rules of basic algebra,
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Howdy! Here are a few very handy rules of algebra. These basic rules are useful for everything from figuring out your gas mileage to acing your next math test — or even solving equations from the far reaches of theoretical physics. Happy calculating!

Algebra Rule 10

Convert a division between two fractions into a fraction of two multiplications

$${({a \over c})\over({b \over d})} = {ad \over bc}$$
Description:

This is a combination of rule 3 and rule 4.

$${({4 \over 5})\over({2\over1})} = {0.8 \over 2} = {4 \over 10} = {4*1 \over 2*5}$$
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