SOLUTION: How wide a border of uniform width should be added to a rectangle that is 8 ft by 12 ft in order to double the area?

Question 870992: How wide a border of uniform width should be added to a rectangle that is 8 ft by 12 ft in order to double the area?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Let the width be x
..
Length of rectangle 12 feet
width of rectangle 8 feet

Area = 96 m^2
Area of plot 192 m^2
length of rectangle & plot 12 + 2 x
width of rectangle & plot 8 + 2 x

( 12 + 2 x ) ( 8 + 2 x ) + -96 = 192

96 + 24 x + 16 x + 4 X^2 + -96 = 192
4 X^2 + 40 x -192 =0
4x^2-16x+56x-192=0
4x(x-4)+56(x-4)=0
(x-4)(4x+56)=0
x=4 OR -14
ignore negative
width = 4 feet
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