Question 180813
Solve Variation Problem 
The cost of pipe at Home Depo varies jointly as the length and
diameter of the pipe. 
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c = k*[Ld]
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If 20 feet of 0.5 inch diameter pipe
costs $36.60
Solve for "k":
36.60 =  k[20*0.5]

k = 36.60/10 = 3.66
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Equation:
c = 3.66[Ld]
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, then what is the cost of 12 feet of 0.75 inch
diameter pipe?
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c = 3.66[12*0.75]
cost = 3.66*9
cost = $32.94
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Cheers,
Stan H.