Question 1188078:  Suppose f varies directly as the square of m, and inversely as j. Also, if f=36 when m=2 and j=10. Find f, if m=4 and j=6. 
 Answer by Theo(13342)      (Show Source): 
You can  put this solution on YOUR website! f varies directly as the square of m and inversely as j.
 
 
if f = 36 when m = 2 and j = 10, find the value of f when m = 4 and j = 6.
 
 
the formula is f = k * m^2 / j.
 
 
when f = 36 and m = 2 and j = 10, the formula becomes:
 
 
36 = k * 2^2 / 10.
 
 
solve for k to get:
 
 
k = 36 * 10 / 2^2 = 90.
 
 
k is the constant of variation. 
it does not change it's value in the equation, while all the other variables can change their value.
 
 
when m = 4 and j = 6, the formula becomes:
 
 
f = k * m^2 / j becomes:
 
 
f = 90 * 4^2 / 6.
 
 
solve for f to get:
 
 
f = 240.
 
 
that's your solution.
 
 
 
 
 
 
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