SOLUTION: Length of a rectangle is x-3 and width is 5x+4. The perimeter of this rectangle is 74cm. Write down an equation for the perimeter.

Algebra ->  Rectangles -> SOLUTION: Length of a rectangle is x-3 and width is 5x+4. The perimeter of this rectangle is 74cm. Write down an equation for the perimeter.      Log On


   

Question 1059553: Length of a rectangle is x-3 and width is 5x+4.
The perimeter of this rectangle is 74cm. Write down an equation for the perimeter.
Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!
Perimeter of a rectangle is width+length+width+length (imagine walking around the rectangle, you will see the width twice & length twice), or more simply: Perimeter = 2(width)+ 2(length) = 2(width+length).
Length is given as x-3
Width is given as 5x+4
We were given perimeter = 74cm:
+2+%28%28x-3%29%2B%285x%2B4%29%29+=+74+
+2x-6%2B10x%2B8+=+74+
+12x%2B2+=+74+
+12x-72+=+0+
--
Answer:
+12x-72+=+0+
—
We could solve for x above (x=6), but it is not clear what x represents.
Let's check the answer using x=6: length=6-3 = 3, width = 5*6+4 = 34
2*(3+34) = 2*(37) = 74 so at least we have the correct relationship.
—
The question was to provide an equation for the perimeter. Technically, the answer could've been given as P(x) = 2[(x-3) +(5x+4)] ... simplified to P(x) = 12x+2 as that is actually more of an expression of the perimeter as a function of x. In this case, the information that the perimeter=74 is superfluous.