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Math Help - Percentage Change

  1. #1
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    Percentage Change

    On Sept 1, price of gas was $2.75/gallon, $3.25/gallon on Oct 1 and back down to $2.75/gallon on Nov 1.

    Express (a) and (b) answers in both dollar and percentage values. (c) in percentage points and (d) in percent.

    Between Sept 1 and Oct 1, price increased by _(a)__ .
    Between Oct 1 and Nov 1, price decreased by __(b)__ .

    On May 16 2000, the US federal reserve increased its target for the federal funds from 6.00% to 6.50%. This change of _(c)_ means that the Fed raised its target by approx _(d)_.
    (a) $0.50 or 18.18%
    (b) $0.50 or 15.38%
    (c) 0.25 percentage points
    (d) 8.33%

    I'm helping my sister with her homework and I'm not sure if she expressed the percentages properly.
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  2. #2
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    percent change = \frac{present - prior}{prior} \times 100
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  3. #3
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    That is why, although the actual changes in (a) and (b) are the same, the percentage changes are different: what was "prior" is different so the while the numerators are the same the denominators are different.

    The change for (c) is obviously 6.50- 6.00= 0.50 percentage points, not 0.25. What that a typo? Because (d) is correct and I don't see how you could get (d) with a wrong answer for (c)!
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