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Math Help - Percents question

  1. #1
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    Percents question

    Here's my problem I'm working on:
    Jennifer's best long jump distance increased by 10% from 1990 to 1991 and by 20% from 1991 to 1992. By what percent did her best long jump distance increase from 1990 to 1992?

    The answer isn't 30 but 32. How can I figure this??
    Last edited by mr fantastic; March 19th 2010 at 05:10 PM. Reason: Restored deleted question.
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  2. #2
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    Quote Originally Posted by sarahh View Post
    Here's my problem I'm working on:
    Jennifer's best long jump distance increased by 10% from 1990 to 1991 and by 20% from 1991 to 1992. By what percent did her best long jump distance increase from 1990 to 1992?

    The answer isn't 30 but 32. How can I figure this??
    The simplest way to handle percentages is to convert to actual numbers!

    Assuming her 1990 long jump distance was "100" (just because that is easy to use percents on- the actual figure doesn't matter), 10% of 100 is 10 so her distance in 1991 was 110. 20% of the is 110*.2= 22 so in 1992 her distance as 110+ 22= 132. Now, 132/100= 1.32 or her distance in 1992 was 132% of her distance in 1990- 32% better.

    (It's not 10+ 20= 30 because the second percentage was not "of" the same amount as the first.)
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