SOLUTION: a rectangle is three times as long as it is wide. If its lenght and width are both decreased by 2 cm, its area is decreased by 36cm(2). Find its original dimensions. Make a sketch.

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: a rectangle is three times as long as it is wide. If its lenght and width are both decreased by 2 cm, its area is decreased by 36cm(2). Find its original dimensions. Make a sketch.      Log On


   

Question 65331: a rectangle is three times as long as it is wide. If its lenght and width are both decreased by 2 cm, its area is decreased by 36cm(2). Find its original dimensions. Make a sketch.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
3x%2Ax+=+A
3x%5E2+=+A
%283x+-+2%29%28x+-+2%29+=+A+-+36
3x%5E2+-+8x+%2B+4+=+A+-+36
substitute A for 3x%5E2
A+-+8x+%2B+4+=+A+-+36
subtract A from both sides
-8x+%2B+4+=+-36
8x+=+36+%2B+4
8x+=+40
x+=+5
A+=+3%2A5%5E2
A+=+75 cm2 answer
check
%283x+-+2%29%28x+-+2%29+=+A+-+36
%283%2A5+-+2%29%285+-+2%29+=+A+-+36
13%2A3+=+A+-+36
A+=+39+%2B+36
A+=+75
OK