Omnimaga

General Discussion => Other Discussions => Math and Science => Topic started by: Munchor on February 15, 2011, 04:15:04 pm

Title: 3 simple rule - something
Post by: Munchor 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?

Title: Re: 3 simple rule - something
Post by: Happybobjr on February 15, 2011, 04:19:53 pm

Do you mean x=4?
If so i think you mean cross-multiplying.

Side note:  Is the irc down?

Title: Re: 3 simple rule - something
Post by: Fast Crash on February 15, 2011, 04:31:45 pm

Yes the irc is down

Title: Re: 3 simple rule - something
Post by: jnesselr 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. ;-)

Title: Re: 3 simple rule - something
Post by: Happybobjr on February 15, 2011, 10:04:01 pm

Opps, only looked at the last parts.

Title: Re: 3 simple rule - something
Post by: PeonHero on February 15, 2011, 10:21:45 pm

Cross multiplying was such an easy topic in school, easy on the calculator too.

Title: Re: 3 simple rule - something
Post by: apcalc 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" :)

Title: Re: 3 simple rule - something
Post by: Munchor on February 16, 2011, 02:55:24 pm

"Cross multiplying"

Thanks ;D