SOLUTION: Suppose W varies directly as x and y and inversely as Z, and W=48 when X=2, Y=8 and Z=12. Find W when X=12, Y=6 and Z=24.

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Question 36176: Suppose W varies directly as x and y and inversely as Z, and W=48 when X=2, Y=8 and Z=12. Find W when X=12, Y=6 and Z=24.
Answer by kev82(151) About Me  (Show Source):
You can put this solution on YOUR website!
Hi,
X has gone from 2 to 12, so it has multiplied by 6.
Y has gone from 8 to 6 so has been multiplied by 3/4
Z has gone from 12 to 24 so has multipled by 2.
W varies directly in X and Y, so whatever we do to them is done to W. But it varies inversly in Z so whatever we do to Z, we do the opposite. Therefore W has changed by 6 * 3/4 * 1/2 = 2.25. So the new value for W is 48 * 2.25 = 108.
The other way to do this is say W=kXY%2FZ and use the original data to find k then put the new values in. If you try that you should get k as 36.
Hope that helps,
Kev.