Designinga Dumpster
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Designinga Dumpster
Theproject will be carried out by first identifying a dumpster in theresidential area and all its dimensions measured and recorded. Themain aim of the project is to design a cost-efficient dumpster withthe same volume. The design will be carried out basing on Chapter14.7 of the textbook on establishing minimum and maximum values. Theproject entails developing a total cost equation, calculating partialderivatives and determining the critical points.
Calculatingthe volume of the dumpster
                           Volumeof the dumpster= Total area of faces * height of dumpster
Findingthe area of the faces:
(referto the diagram of dumpster at the end of this project for dimensions)
Area=length *width
Areaof the first face (i) = 0.5*9*9 = 40.5
Areaof the second face (ii) = 9*63 = 567
Areaof the third face (iii) = 72*43.5 = 3132
Areaof the fourth face(IV) = 14.5*29.5 = 427.75
Areaof the fifth face (v) = .5*42.5*34.9 = 71.6
Areaof the sixth face (VI) = 7.7*29.5*.5 = 113.58
Totalarea = 5022.43
Volumeof the dumpster (V):
V=5022.43*72 = 361,615 in3or209.27 ft­3
Determiningthe total cost:
Thesides, back and front are created from 12-gauge steel material whichcosts $0.70 per square foot, the base will be constructed from10-gauge steel material estimated to costs $0.90 per square foot alid cost $50 and the welding cost per foot for material inclusiveof labor will be $0.18.
TotalCost Equation:
T=1.4xz + 1.4yz + .9xy + .32x + .32y + .64z + 50
Where:
T=Total cost
x=Width,y=Length, and z=Height. (All the dimensions are based on a3-dimentional graph)
Thedumpster volume= 209ft3,Hence:
xyz= 209 or z  =  209/(xy)
Reducingthe equation into 2 variables, z value will be substituted into thetotal cost equation.  Thus:
OverallCost = 1.4(209/y) QUOTE +1.4(209/x)+0.9xy+0.32x+0.32y+0.64(209/(xy))+50
Determiningpartial derivatives of the total cost equation
Fromtotal cost equation, we get partial derivative fxand fy.
fx=-292.6/(x2)+0.9y+0.32-133.76/(yx2)
fy==-292.6/(y2)+0.9y+0.32-133.76/(xy2)
Determiningthe critical points
First,partial derivative equations are simplified and equated to zero.
fx, 0=-292.6y+0.9x2y2+0.32x2y-133.76
fy.0=292.6x+0.9x2y2+0.32y2x-133.76
Then,both sides are multiplied by 10 and subtracting gives:
(0=-2926y+9x2y2+3.2x2y-1337.6) – 0=-2926x+9 x2y2+3.2y2x-1337.6)
0=-2926y+2926x+3.2 x2y-3.2 y2x
Furthersimplifying the resulting equation and equating it to 0, we finallyget:
2926(x-y)+3.2xy(x-y) =0
(2926+3.2xy)(x-y)=0,2926+3.2xy=0 0r x-y= 0 where (x=y)
Testingfor feasibility
Thesolution, x=-2926/ (3.2y) is not feasible. For a solution to befeasible x and y must be greater than zero.
Thevalue of z= 6ft is selected to get a feasible solution. Hence, aftersubstituting in z=209/ (xy), the new values of x=y, will be 5.901.Using the above values the estimated total cost will be $ 188.12.
Acrucial factor to consider in this study is that a dumpster of arectangular shape was used to solve a minimizing equation. Theapproach utilized in this particular design is much more expensive ascompared to the original plan and a Construction firm may find itunfeasible to use this model.
Diagrammaticrepresentation of a dumpster