SOLUTION: pls help me to answer: z is directly proportional to x and inversely to the square of y. what is the percent of z if x is increased by 20% and y is decreased by 40%?

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Question 1134024: pls help me to answer: z is directly proportional to x and inversely to the square of y. what is the percent of z if x is increased by 20% and y is decreased by 40%?
Found 2 solutions by Alan3354, MathLover1:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
z is directly proportional to x and inversely to the square of y. what is the percent of z if x is increased by 20% and y is decreased by 40%?
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z = k*x/y^2
z2 = k*(1.2x)/(0.6y)^2 = z*(1.2/0.36) = 10z/3
An increase of 7z/3 = 233.33...%

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

Given z+=+%28x%2Fy%5E2%29
Hence+z+=+%28x%2Fy%5E2%29 assuming proportionality constant as 1.
x increase by 20% and y decreases by 40%
Hence z value becomes:
z+=+1.20x%2F%28%281-0.40%29y%29%5E2+=+1.20x%2F%280.60y%29%5E2
Change in z value
= +1.20x%2F%280.36y%5E2%29-%28x%2Fy%5E2%29
= %282.33333x%29%2Fy%5E2

Increase in z% =%28%282.33333x%29%2Fy%5E2%29%2F%28x%2Fy%5E2%29%2A100
=2.33333%2A+100+=+233.333%