Question 1186202
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If you need a formula to express the relationship between x, y, and z, then you can determine the constant of variation as the other tutor did.  You would probably want to do that if you were going to use the formula for a large number of different parameter values.<br>
But if you only need to solve the problem for the one set of new parameters, then you don't have to do all that work.<br>
z varies directly as x; x changes from 4 to 8, an increase by a factor of 2; so z increases by a factor of 2.<br>
z varies inversely as the square of y; y changes from 4 to 10, an increase by a factor of 5/2; so z decreases by a factor of (5/2)^2.<br>
{{{(12)(2)(1/(5/2)^2)=24(4/25)=96/25=3.84}}}<br>
ANSWER: When x = 8 and y = 10, z = 96/25 or z = 3.84<br>