### Author Topic: 3 simple rule - something  (Read 3471 times)

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#### Munchor

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##### 3 simple rule - something
« on: February 15, 2011, 04:15:04 pm »
In portuguese, we have something called 'Regra de 3 Simples', and I'd like to know what it is called in English:

1  -   4
2  -   x

x = (2*4)/1
x = 8

It's used in direct proportions, what's it called, do you have a name for it?
« Last Edit: February 16, 2011, 02:55:06 pm by Scout »

#### Happybobjr

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##### Re: 3 simple rule - something
« Reply #1 on: February 15, 2011, 04:19:53 pm »
Do you mean x=4?
If so i think you mean cross-multiplying.

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#### Fast Crash

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##### Re: 3 simple rule - something
« Reply #2 on: February 15, 2011, 04:31:45 pm »
Yes the irc is down

#### jnesselr

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##### Re: 3 simple rule - something
« Reply #3 on: February 15, 2011, 09:48:34 pm »
Cross multiplying is what it is called, yes.  And x does in fact equal 8, it's just that he did x=(2*4)/2 when it should have been x=(2*4)/1.  He knew what he was doing, he just didn't. ;-)

#### Happybobjr

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##### Re: 3 simple rule - something
« Reply #4 on: February 15, 2011, 10:04:01 pm »
Opps, only looked at the last parts.
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#### PeonHero

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##### Re: 3 simple rule - something
« Reply #5 on: February 15, 2011, 10:21:45 pm »
Cross multiplying was such an easy topic in school, easy on the calculator too.
There are a lot of<a href="http://justmegawatt.com/images/youdidntknow"> Things you didn't know </a>about until you clicked that link.

#### apcalc

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##### Re: 3 simple rule - something
« Reply #6 on: February 15, 2011, 10:23:35 pm »
To confuse people, I always like saying, "Solve using the fact that the product of the means is equal to the product of the extremes"
« Last Edit: February 15, 2011, 10:23:46 pm by apcalc »

#### Munchor

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##### Re: 3 simple rule - something
« Reply #7 on: February 16, 2011, 02:55:24 pm »
"Cross multiplying"

Thanks