SOLUTION: The variable Z is directly proportional to X, and inversely proportional to Y. When X is 6 and Y is 6, Z has the value 12. What is the value of Z when X = 13, and Y = 10

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Question 981067: The variable Z is directly proportional to X, and inversely proportional to Y. When X is 6 and Y is 6, Z has the value 12.
What is the value of Z when X = 13, and Y = 10

Found 2 solutions by rothauserc, ikleyn:
Answer by rothauserc(4718)   (Show Source): You can put this solution on YOUR website!
Z = k * X / Y where k is the constant of proportionality
when Z = 12, X = 6, Y = 6 we have
12 = k * 6 / 6
k = 12
********************************************************
Z = 12 * 13 / 10
Z = 156 / 10
Z = 15.6

Answer by ikleyn(52786)   (Show Source): You can put this solution on YOUR website!

The fact that  "the variable  Z  is directly proportional to  X,  and inversely proportional to  Y"  (which is the given condition)  means that

= ,

where   = const  (a constant value).  If you substitute  ,    and    into this formula,  you will get

= = .

Hence,   = .

Thus our formula for    is

= .

Now,  if you substitute    and    into the last formula,  you will get

= = = = .

It is the answer to your question.


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