Geometry

The area of a 300' by 400' rectangle is doubled by adding a strip of width around the perimeter. Approximately how wide is that strip?

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  1. old area = 300*400 = 120 000
    new area = 240 000

    (300+2x)(400+2x) = 240000
    120000+1400x + 4x^2 = 240000
    simplify and divide by 4.

    x^2 + 350x - 30000 = 0
    x = (-350 ± √242500)/2
    = appr 71.22 or some negative which we will reject

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