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A 12 cm by 16 cm picture is mounted with border of uniform width on a rectangular frame. If the total area of the border is 288 cm², what is the length of the side of the frame?

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Cheahjimmyviz
let x = side of the border in cm added to the length & width
of the picture
thus new length of picture =  16 +2x
                 width of picture  =    12 +2x
(16+2x)(12+2x) =    (12*16)+288  =  480
 192 +32x +24x +4x² =  480
  4x² +56x - 288 =  0
     x² + 14x -72 = 0              /  ÷ 4
     (x +18)(x -4) = 0
       x = -18 0r  4
thus the new length of the picture = 16 + 2x =  24cm
                      width of the picture    = 12 +2x =  20cm





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