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Homework Help: Find proportions when there are 2 variables

  1. Sep 5, 2010 #1
    a is proportional to square root of (b *t2)
    a is proportional to 1/c3

    a is 5, when b = 9, t = 2, c = 3

    Find a' when b'=25, t'=2, c'=5

    My attempt:

    = (25 root 5/12 root 3) 5

    I think my steps are wrong, can someone help me!?
  2. jcsd
  3. Sep 5, 2010 #2


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    Science Advisor
    Homework Helper

    I think you are getting confused by the a / a' notation.

    Let's start with this part. This means, that a contains both those factors, so you can write it as
    [tex]a(b, t, c) = \frac{\sqrt{b t^2}}{c^3} \cdot k[/tex]
    The k here is some constant number (the proportionality factor). Note that I have written the left hand side as if it were a function of b, t and c.

    Now, you know that a(b = 9, t = 2, c = 3) equals 5, you can use that to calculate the proportionality constant k.
  4. Sep 5, 2010 #3
    Thank you so much for the help :)
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