Question 205709
(A)  Cost = .10*Area + .25* Perimeter
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If l=30,,& w=20,,,,Area = L*W,,,,Per = 2L + 2W
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cost = .10(30*20) +.25( 2*30+2*20)
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Cost = .10(600) + .25(100)
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Cost = 60 + 25 = $ 85
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(B)  Let L=40,,,,find  W
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Cost = .1A + .25P = .1(40*W) + .25( 2*40+2*W)= 4W + 20 + .5W = 4.5 W +20
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If  Cost  is  $ 85,,85=4.5W +20,,,,65 = 4.5 W,,,,W= 14.444 in.
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(C),,,, Cost  = .1Area + .25Per
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C= .1(L*W) + .25(2L+2W)
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C= .1LW + .5L +.5W
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(D)  C-.5W = L (.1W +.5)
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(C-.5W) / (.1W +.5) = L,,,,,,checking  with  original(20*30=$85),,,ok