SOLUTION: One of the side of a rectangle is 3m shorter than the other one. Find the sides of the rectangle if we know that if we increase every side with 1m, the surface of the rectangle wil

Algebra ->  Surface-area -> SOLUTION: One of the side of a rectangle is 3m shorter than the other one. Find the sides of the rectangle if we know that if we increase every side with 1m, the surface of the rectangle wil      Log On


   



Question 981402: One of the side of a rectangle is 3m shorter than the other one. Find the sides of the rectangle if we know that if we increase every side with 1m, the surface of the rectangle will be increase with 18 meter square.
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
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L=length; W=width=L-3m
Area before increase=(L)(W)=(L)(L-3m)=L^2-3L
Area after increase=(L+1m)(L-3m+1m)=(L+1m)(L-2m)=L^2-L-2m
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Area after increase-area before increase=18m^2
%28L%5E2-L-2m%29-%28L%5E2-3L%29=18m%5E2
L%5E2-L-2m-L%5E2%2B3L=18m%5E2
2L-2m=18m%5E2
2L=20
L=10m The original length was 10 meters.
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W=L-3m=10m-3m=7m The original width was 7 meters.
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CHECK:
Area after 1m increase-area before 1m increase=18m^2
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%28L%2B1m%29%28W%2B1m%29-%28L%29%28W%29=18m%5E2
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%2810m%2B1m%29%287m%2B1m%29-%2810m%29%287m%29=18m%5E2
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%2811m%29%288m%29-70m%5E2=18m%5E2
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88m%5E2-70m%5E2=18m%5E2
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18m%5E2=18m%5E2