SOLUTION: a rectangular picture 12cm by 10cm has a border of uniform width. if the area of the border is 168cm squared, how wide is the border

Question 694717: a rectangular picture 12cm by 10cm has a border of uniform width. if the area of the border is 168cm squared, how wide is the border
Answer by sachi(548) (Show Source): You can put this solution on YOUR website!
let the uniform border is b cm
so the picture 12cm by 10cm will be (12+2b)cm by (10+2b)cm with border
now the area of the border = area of picture with border-are of picture
or (12+2b)*(10+2b)-12*10=168 given
or 120+2b(12+10)+4b^2-120=168
or 4b^2+44b-168=0
or b^2+11b-42=0
or b^2+14b-3b-42=0
or b(b+14)-3(b+14)=0
or (b-3)(b+14)=0
or b=3 or -14 (discarded)
so the width of the border is 3 cms
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