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Math Help - Dividing ratios.

  1. #1
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    Dividing ratios.

    A question has come up on a mock exam and i'm not sure if i have done it correctly so please can you tell me if i have done it wrong or if it is right?

    Peter and Margaret's ages are in the ratio 4:5. If Peter is 16 years old, how old is Margaret?

    Peter = 4/9
    so 1/9 is 16 divided by 4 = 4
    4 x 5 = 20
    Margaret is 20.

    Thank you in advance
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  2. #2
    MHF Contributor
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    you have the right answer
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  3. #3
    Super Member Quacky's Avatar
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    Quote Originally Posted by mollyx View Post
    A question has come up on a mock exam and i'm not sure if i have done it correctly so please can you tell me if i have done it wrong or if it is right?

    Peter and Margaret's ages are in the ratio 4:5. If Peter is 16 years old, how old is Margaret?

    Peter = 4/9
    so 1/9 is 16 divided by 4 = 4
    4 x 5 = 20
    Margaret is 20.

    Thank you in advance
    Correct, but there is an easier approach.

    The question is essentially saying:

    4:5=16:?

    And, as you know that 4 x 4 = 16
    To find out the missing value, just do the same thing to the other side of the ratio:
    5 x 4 = 20
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