SOLUTION: The variable Z is directly proportional to X, and inversely proportional to Y. When X is 12 and Y is 4, Z has the value 57. What is the value of Z when X = 18, and Y = 10 Th

Algebra ->  Rational-functions -> SOLUTION: The variable Z is directly proportional to X, and inversely proportional to Y. When X is 12 and Y is 4, Z has the value 57. What is the value of Z when X = 18, and Y = 10 Th      Log On


   

Question 981813: The variable Z is directly proportional to X, and inversely proportional to Y. When X is 12 and Y is 4, Z has the value 57.
What is the value of Z when X = 18, and Y = 10
This is what I've tried
z=kx/y
57=k*12/4=3k
k=171
z=171*18/10
z=307.8
Answer by josgarithmetic(39627) About Me  (Show Source):
You can put this solution on YOUR website!
Your first sentence: Z=kX%2FY

Find a formula for k.
k=ZY%2FX

Your second sentence indicates:
k=57%2A4%2F12
k=57%281%2F3%29
k=19

The formula for Z is this:
highlight%28Z=19Y%2FX%29