A farmer needs to enclose three sides of a field with a fence (the fourth side is a cliff wall). The farmer has 43 feet of fence and wants the field to have an area of 221 sq-feet. What is the Length and the Width?
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Verified answer
Let the width be w and the length be l.
=> 2w + l = 43
and lw = 221
=> w(43 - 2w) = 221
=> 2w² - 43w + 221 = 0
i.e. (2w - 17)(w - 13) = 0
so, w = 17/2 or 13
=> width 8.5 feet and length 26 feet
or width 13 feet and length 17 feet.
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Perimeter = 2x +y = 43
Area = 2xy = 221
y = 43 - 2 x
2x (43 -2x ) = 221
86 x -4 x^2 - 221 = 0
4 x^2 - 86 x + 221 =- 0
x^2 - 21.5 x + 55.25 = 0
X= + 21.5/2 +/- 1/2 (21.5^2 - 4x55.25)^1/2
X = 18.5 y = 6
Check: 2x + y = 2 x 18.5 + 6 = 43
2xy = 2x 18.5 x 6 = 222
L * W = 221 : eqn1
L + 2 W = 43: eqn2
L = 43 - 2 W from eqn 2
(43-2W)(W) = 221 sub in eqn 1
43 W - 2 W^2 = 221
2 W^2 - 43 W + 221 = 0
(2 W -17 )(W-13 ) = 0
W = 17/2: L = 43-(17/2)2 = 26
W = 13 ; L = 43-2(13) = 43-26 = 17
ok he have 3 sides and their length is 43 feets let Length = x and width = y
and that he has 2x + y = 43
Since Area is 221 So xy = 221
x = 221/y By Substituting in the first one
2(221/y) + y = 43 Multiply y
442 + y^2 = 43y
y^2 - 43y + 442 = 0
(y-26)(y-17) = 0
So y = 26 or 17 So the Width = 26Feets or 17 Feets
When Width = 26 , Length = 8.5
When Width = 17 , Length = 13