SOLUTION: I am trying to find a solution to a problem for my 7th grader that has me confused. I have a rectangle. The long side "length" is 3x + 4 and the short side "width" is x - 2

Algebra ->  Points-lines-and-rays -> SOLUTION: I am trying to find a solution to a problem for my 7th grader that has me confused. I have a rectangle. The long side "length" is 3x + 4 and the short side "width" is x - 2      Log On


   

Question 1108651: I am trying to find a solution to a problem for my 7th grader that has me confused.
I have a rectangle.

The long side "length" is 3x + 4 and the short side "width" is x - 2.
The perimeter is 20.
I have to figure the value of x.
I came up with the value of 2 for x.
If that is correct that the rectangle would have 2 sides of 10cm
And 2 sides of 0. Please help.
_____3x_+4_________
|
|x -2
|_________________|
P = 20. Solve for x

Found 3 solutions by ikleyn, addingup, TeachMath:
Answer by ikleyn(52914) About Me  (Show Source):
You can put this solution on YOUR website!
.
Perimeter = L + W + L + W


20 = (3x+4) + (x-2) + 3x+4) + (x-2),

20 = 8x + 4,

20 - 4 = 8x  ====>  8x = 16  ====>  x = 16%2F8 = 2.


Answer.  x = 2.

Solved.


Answer by addingup(3677) About Me  (Show Source):
You can put this solution on YOUR website!
Perimeter = 2L + 2W. Agreed? If so:
2(3x + 4) + 2(x - 2) = 20
Distributive Law of multiplication:
6x + 8 + 2x - 4 = 20
Group similar:
6x + 2x + 8 - 4 = 20
8x + 4 = 20
Subtract 4, both sides:
8x = 16
x = 2
-------------------------------
Check:
2(3 * 2 + 4) + 2(2 - 2) = 20
2(6 + 4) + 4 - 4 = 20
12 + 8 + 4 - 4 = 20
20 + 0 = 20 Correct

Answer by TeachMath(96) About Me  (Show Source):
You can put this solution on YOUR website!
Something's wrong with one or both expressions, or the length of the perimeter. x is definitely equal to 2, but it doesn't make sense since that will make the shorter side 0, and which will leave 2 lines measuring 10 units each. That's not a rectangle.