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Math Help - percent change (Interesting)

  1. #1
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    percent change (Interesting)

    Carmen is 15% lighter than Mary and Thomas is 25% heavier than Carmen. Between Mary and Thomas, who is heavier? By what Percentage?

    Solution:
    (1) Let Mary weight = 1, Carmen weight =0.85 then Thomas = 0.85*1.25=1.0625
    so, Thomas is heavier. He is heavier than Mary by 6.25%

    (2) Let Carmen weight = 1 then Mary = 1.15 and Thomas =1.25
    so, Thomas is heavier. He is heavier than Mary by 8.7%

    Please let me know why there is different anwser?
    Thanks so much!!
    Last edited by tinng; November 28th 2008 at 10:05 PM.
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  2. #2
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    Quote Originally Posted by tinng View Post
    Carmen is lighter than Mary and Thomas is 25% heavier than Carmen. Between Mary and Thomas, who is heavier? By what Percentage?

    Solution:
    (1) Let Mary weight = 1, Carmen weight =0.85 then Thomas = 0.85*1.25=1.0625
    so, Thomas is heavier. He is heavier than Mary by 6.25%

    (2) Let Carmen weight = 1 then Mary = 1.15 and Thomas =1.25
    so, Thomas is heavier. He is heavier than Mary by 8.7%

    Please let me know why there is different anwser?
    Thanks so much!!
    ============================================
    Tinng, I got it.
    (2) is correct. if let carmen weight =1.
    (1) Carment weight = ( 1/1.15) = 0.869565 then Thomas = 0.869565 * 1.25= 1.0869565
    So, Thomas is heavier than Mary by 8.7%.
    Last edited by 2976math; November 28th 2008 at 10:15 PM.
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  3. #3
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    Quote Originally Posted by 2976math View Post
    ============================================
    Tinng,
    Question is not clear, Carmen is lighter than Mary by how much?

    Sorry~~
    Carmen is 15% lighter than Mary
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  4. #4
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    Smile

    Quote Originally Posted by tinng View Post
    Carmen is 15% lighter than Mary and Thomas is 25% heavier than Carmen. Between Mary and Thomas, who is heavier? By what Percentage?

    Solution:
    (1) Let Mary weight = 1, Carmen weight =0.85 then Thomas = 0.85*1.25=1.0625
    so, Thomas is heavier. He is heavier than Mary by 6.25%

    (2) Let Carmen weight = 1 then Mary = 1.15 and Thomas =1.25
    so, Thomas is heavier. He is heavier than Mary by 8.7%

    Please let me know why there is different anwser?
    Thanks so much!!
    The point is (2) Let Carmen weight = 1 then Mary = 1.15
    mean mary is heaver than Germen 15%,but not Garmen is lighter than mary 15%, is lighter than mary 0.15/1.15=13%
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  5. #5
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    Quote Originally Posted by tinng View Post
    Carmen is 15% lighter than Mary and Thomas is 25% heavier than Carmen. Between Mary and Thomas, who is heavier? By what Percentage?

    Solution:
    (1) Let Mary weight = 1, Carmen weight =0.85 then Thomas = 0.85*1.25=1.0625
    so, Thomas is heavier. He is heavier than Mary by 6.25%

    (2) Let Carmen weight = 1 then Mary = 1.15 and Thomas =1.25
    so, Thomas is heavier. He is heavier than Mary by 8.7%

    Please let me know why there is different anwser?
    Thanks so much!!
    (1) Nice work.

    (2) If carmen = 1, then Mary would not be 1.15, as 15% of 1.15 is not 0.15. You would need to find the number which, when 15% of it is taken away, results in 1. But this is not necessary as your first answer is correct.
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