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a is directly proportional to m and n^2, and inversely proportional to y^3. If a=9 when m=2, n=8 and y=4, solve for a when m=6, n=7 and y=3.

 

I know the formula for direct and inverse proportions (y=kx and y=k/x), but I'm not entirely sure what to do with this problem. When I try solving individually for a k with a and m, a and n, and a and y, the 'k' values are different, so I don't know how to preceed.

 Jan 12, 2022
 #1
avatar+36434 
+2

a is directly proportional to m and n^2, and inversely proportional to y^3.  

  means   a = k mn^2 / y^3

     or    a y^3 / (mn^2) = k    a constant

             9 (4^3) / (2(8^2)) = k

                k = 4.5

 

       then    a  (3)^3 / ( 6(7^2)) = k = 4.5      solve for 'a'

 Jan 12, 2022
 #2
avatar+28 
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Oh, I get it now! So a would be 49, right?

caramel  Jan 13, 2022
 #3
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Yes, correct...a =49

Guest Jan 13, 2022

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