Posted by **chrissy** on Wednesday, August 1, 2007 at 4:49pm.

oook that site didnt help much I dont need to know how to suck up to my teacher. I need to know how to set up a ratio, can someone help me??

The format for ratios is # : # :: # : #

Example 1: 2 :: 2 : ?

1 is one half of 2... so 2 would be one half of ? Four , of course.

Chrissy, here is an excellent site on how to set up ratios.

http://cstl.syr.edu/FIPSE/Decunit/ratios/ratios.htm
thank you ok that sounded simple. but is it always one half of a number or..can you give me an example or a problem and solve it out???

oooo thanks for the site. it will help me alot!

I'm sorry, the site I thought I posted wasn't the same one that was posted.

GuruBlue has given you an excellent site.

The problem you had stated that 2 inches on the blueprint equals 5 feet in the actual room. The problem asks the length of the actual measurement when it's 7 1/2 inches long on the blueprint. Here's the ratio I set up:

2 inches is to 5 feet as 7 1/2 inches is to x (the actual length).

This is shown as:

2 / 5 as 7 1/2 / x

We cross multiply the top of the first fraction with the bottom of the second fraction.

2x = 5 (7 1/2)

2x = 37.5

x = 18.75 = 18 3/4

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