SOLUTION: HI, A wire of length 40 inches is to be cut into two pieces, each of which will be used to form a circle. Suppose we will be charged $2 for each square inch of area enclosed by th

Algebra ->  Finance -> SOLUTION: HI, A wire of length 40 inches is to be cut into two pieces, each of which will be used to form a circle. Suppose we will be charged $2 for each square inch of area enclosed by th      Log On


   



Question 864949: HI,
A wire of length 40 inches is to be cut into two pieces, each of which will be used to form a circle. Suppose we will be charged $2 for each square inch of area enclosed by the first circle, and $1 for each inch in the second circle's circumference. Find the lengths of the two pieces of wire which will
minimize the total cost.

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
A wire of length 40 inches is to be cut into two pieces, each of which will be used to form a circle. Suppose we will be charged $2 for each square inch of area enclosed by the first circle, and $1 for each inch in the second circle's circumference. Find the lengths of the two pieces of wire which will
minimize the total cost.
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C = length of wire in the 1st circle ($2 per sq inch)
C+=+2pi%2Ar
--> r+=+C%2F2pi
Area+=+pi%2Ar%5E2+=+pi%2A%28C%5E2%2F4pi%5E2%29+=+C%5E2%2F4pi
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--> $1/inch of 40 - C for the 2nd circle
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Price = 2%2AC%5E2%2F4pi+%2B+40+-+C
P(C) = C%5E2%2F2pi+-+C+%2B+40
P'(C) = C%2Fpi+-+1+=+0
C = pi inches for the 1st circle
40 - pi inches for the 2nd