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December 20, 2014

December 20, 2014

Posted by **susie** on Thursday, June 4, 2009 at 5:59pm.

A rancher wants to fence in an area of 2500000 square feet in a rectangular field and then divide it in half with a fence down the middle parallel to one side. What is the shortest length of fence that the rancher can use?

- math -
**Damon**, Thursday, June 4, 2009 at 6:47pmA = a b so b = A/a

P = 2 a + 3 b

P = 2 a + 3 A/a

now A=2.5*10^6

P = 2a + 7.5*10^6/a

dP/da = 0 at in or max

dP/da = 0 = 2 -7.5*10^6/a^2

a^2 = 3.75*10^6

a = 1.936*10^3

then b = 2.5*10^6/1.936*10^3

b = 1.291*10^3

P = 2*a+3*b = 7.745*10^3

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