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An increase of $0,15 on a price of 2,50 is an increse by a fraction

  1. Nov 2, 2007 #1
    an increase of $0,15 on a price of 2,50 is an increse by a fraction of 0.15/2.50=0,06

    expressed as a percentage,therefore a 6% increase

    I don,t understand this

    and why we put 0.15 is numerator
  2. jcsd
  3. Nov 2, 2007 #2


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    Decide which culture you are expressing; either a comma for whole-fraction separation, or a period, dot for whole-fraction separation. Let's use the dot, or "decimal point".

    You can compare the size of price increase to the original or starting price. This comparison can be expressed as a fraction. You put the 0.15 in the numerator because you are looking at how large is the increase compared to the original; otherwise, you could compare the original price to the price increase by putting the 2.50 in the numerator.

    What fraction of the original is the increase? 0.15/2.50
    What fraction of the increase is the original? 2.50/0.15

    Obviously, in the second case, the fraction is actually larger than 1. [two and a half over fifteen hundredths]
  4. Nov 3, 2007 #3
    you mean that percentage is change over the whole
  5. Nov 4, 2007 #4
    I have problem with concept of percentage

    I don't understand it clearly

    please help me

  6. Nov 4, 2007 #5


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    Percentage is the numerator corresponding to a denominator of 100.
    0.06 = 6/100 = 6 %, meaning six percent.
  7. Nov 4, 2007 #6


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    Or, if you would normalize it to 100, how much it would become. This allows for easy comparison.

    Compare it to this example: brand A comes in 50 cl bottles and costs $ 0.60, brand B costs $ 0.45 but it only comes in 33 cl bottles, which one is a better buy?
    One way (the most common, I think) to see this is by converting both quantities to the 1 liter price. I need to bottles of A to make a liter, so A costs $ 1.20 for a liter, while B costs $ 0.45 * (100 / 33) [itex]\approx[/itex] $ 1.36 per liter. So though A is more expensive, it is cheaper in comparison with B.

    Now take this example: in one store the salesman gives me a $ 200 discount on a TV which would normally cost $ 1500, in another store I find a cheaper TV of $ 1300 but I only get $ 125 discount. In which store will I relatively save the most money? Again, we normalize the price of a TV to $ 100. Dividing the price and the discount by 15 on both sides, I would get about $ 13.33 off at one, and (divide by 13) $9.62 at B, if the TV would cost $100. In other words, for each $100 dollar I would spend on the TV, I would get $13.33 discount at one store, and $9.62 at the other one. This is what we mean by saying "I get a 13.33% discount at one store, and 9.62% at the other" (x % being: x on every 100).
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