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Proportions help needed

  1. Apr 13, 2008 #1
    Proportions help needed!!

    Three water masses (I, II, III) are mixed together to form a resultant water mass (R).
    I: T=5 deg C, S=35.50 ppt
    II: T=2 deg C, S=34.50 ppt
    III: T= 1 deg C, S=35.25 ppt
    R: T= 3 deg C, S=35.00 ppt
    What were the relative proportions of I, II, and III that were mixed together to form R?

    Someone please help, I don't even know where to start...
     
  2. jcsd
  3. Apr 13, 2008 #2

    tiny-tim

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    Hi groovayness! :smile:

    In questions like this, start by saying:

    "Let the mass of I be a, of II be b, and of III be c".

    (So the mass of R will be a + b + c.)

    Hint: if a combination of a at 5º, b at 2º, and c at 1º, is at 3º … what formula does that give you connecting a b and c? :smile:
     
  4. Apr 13, 2008 #3
    ok so would the equation be 5a+2b+1c=3(a+b+c)? but then what am i solving for?
    And then where do i factor in the salt concentration (s)?
     
  5. Apr 13, 2008 #4

    tiny-tim

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    Yes, that's right!

    Now put the a's b's and c's together, to make 2a = b+ 2c.

    And then do the same thing for the salt … then you'll have another equation for a b and c, from which you can find the ration b/c. :smile:
     
  6. Apr 13, 2008 #5
    ok i think i got it.

    i got a:b:c is 3.5 : 5 : 1

    is that correct?
     
  7. Apr 14, 2008 #6

    tiny-tim

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    Noo … it should be 5 : 6 : 2.

    Show us your working. :confused:
     
  8. Sep 1, 2008 #7
    Re: Proportions help needed!!

    A spherical balloon is partially blown up and its surface area is measured. More air is then added, increasing the volume of the balloon. If the surface area of the balloon expands by a factor of 9.4 during this procedure, by what factor does the radius of the balloon change?

    If the radius of a sphere is increased by 12 %, by what factor does its surface area increase?
    - By what percentage does its surface area increase?
    - By what factor does the sphere's volume increase?
    - By what percentage does the sphere's volume increase?

    The weight of an object at the surface of a planet is proportional to the planet's mass and inversely proportional to the square of the radius of the planet. Jupiter's radius is 11 times Earth's and its mass is 320 times Earth's. An apple weighs 1.0 N on Earth. How much would it weigh on Jupiter?
     
  9. Sep 2, 2008 #8

    tiny-tim

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