SOLUTION: The variable Z is directly proportional to X, and inversely proportional to Y. When X is 3 and Y is 6, Z has the value 9.5. What is the value of Z when X = 8, and Y = 12

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Question 981073: The variable Z is directly proportional to X, and inversely proportional to Y. When X is 3 and Y is 6, Z has the value 9.5.
What is the value of Z when X = 8, and Y = 12

Found 2 solutions by ikleyn, stanbon:
Answer by ikleyn(52781)   (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  (is 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

= = = (approximately).

It is the answer to your question.


Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
The variable Z is directly proportional to X,
and inversely proportional to Y.
---
Z = K*X/Y
-----------
When X is 3 and Y is 6, Z has the value 9.5.
Solve for "K"::
9.5 = K*3/6
K = 19
------
What is the value of Z when X = 8, and Y = 12
Equation:
Z = 19*X/Y
Z = 19*8/12
Z = (2/3)19 = 38/3 = 12 2/3
---------------
Cheers,
Stan H.
----------------

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