Question 698662
A garden plot 5m by 15m has one of its sides next to a wall. The area of the plot is to be doubled by digging up a strip of uniform width along the other three sides. How wide should the border be?
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 Draw the picture of the garden with the wall on one side.
 Area of the garden = 15*5 = 75 m^2
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 Let the uniform width of the stip be "x".
 Area of the strip = 15x + x(x+5) + x(x+5) = 2x^2+25x
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 Equation:

 

strip area = garden area
 2x^2 + 25x = 75
 2x^2+25x-75 = 0
 (2x-5)(x+15) = 0
 Positive solution: 
x = 5/2 meters