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Fraction,Percent, Ratio Problem

  1. Jan 2, 2007 #1
    Hmm am I posting too many problems? Is there a specific thread where I can post these? =/

    Anyways here goes:
    There are g gallons of paint available to paint a house. After n gallons have been used, then, in terms of g and n, what percent of the paint has not been used?

    a) 100n/g%

    b) g/100n%

    c) 100g/n%

    d) g/(100(g-n))%

    e) (100(g-n))/g%

    Okay, here is the case. I've gotten this problem right the first time, however, I would like a solution from any of you ccers =]

    Here's my solution:
    Well since the total amount is expressed as g, the percent fraction obviously has to be over g(the gallons of paint available). Since n is the number of gallons used, the number of gallons not used would be g-n.

    I'm confused about why you need to multiply it by 100. Is it because you need to convert a fraction in a percentage problem? Haha, I think I answered my own question but anyways...

    I think 100 is put in front because a fraction is expressed in the form of a decimal and in order to make a percent (% is put in front) you need to multiply the fraction by 100 to move it two decimal places up?

    ex: 1/4x 100 = 100/4= 25% same as .25 x 100 =25%?

    Can anyone tell me if this works for all of these types of problems and is universal?? I don't know if I'm doing this right but I'm pretty sure =D
  2. jcsd
  3. Jan 2, 2007 #2


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    Staff Emeritus
    Science Advisor

    Yes, you are correct. WE multiply by 100 since we are turning the fraction into a percentage. (Note that "percent" means "per hundred" and so mulitplying by 100 enables us to then include the % sign.) This does work for all problems.

    In your example, 1/4=(1x100)/4%=25%. Of course, this is the same as 0.25=0.25/100%=25%
  4. Jan 2, 2007 #3
    Wow I never knew that "percent" is acutally "per cent", cent meaning 100 right? ooo wow. hehe math problems are fun.
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