Rossina G. answered 12/05/18
Common Core Experience: Integrated Math Subjects, 10 years tutoring
-First, some guidelines to work out these types of problems:
- Draw a picture and label it
- relate the variables and numbers to each other in a way that makes sense with the story of the word problem
- Solve
-Draw a picture
It should be a rectangle with the longer side labeled "w+2" (the length is 2 more than the width) and the shorter side labeled "w" (width)
-Relate the variable and numbers
Area is 80 -> A = 80
Length = w + 2
Width = w
Area of a rectangle is length times width -> A = lw
-Solve. Now, we just plug in what we know about each of these variables and solve:
A = lw
80 = (w +2 ) (w)
80 = w^2 + 2w
0 = w^2 + 2w - 80
w^2 + 2w - 80 = 0 <-- I just flipped it around because it's easier to understand this way
(w + 10) (w -8) = 0 <--when you have a quadratic, you must factor in order to solve for "w"
w = -10 and w = 8
We only use w=8 because -10 is not a possible width (we do not measure length in terms of negatives!)
Now that we know the width, let's find the length. *Remember, from before Length = w + 2
Length = 8 + 2
Length = 10
-The final answer:
Your dimensions are -> width = 8 and length = 10
You did it!