SOLUTION: If the perimeter of a certain rectangle is 78cm. and the width is 12cm., what is the length? P=2w + 2l So, my equation looks like this: 78 = 12w + 2l (I'm not even sure that'

Algebra ->  Customizable Word Problem Solvers  -> Geometry -> SOLUTION: If the perimeter of a certain rectangle is 78cm. and the width is 12cm., what is the length? P=2w + 2l So, my equation looks like this: 78 = 12w + 2l (I'm not even sure that'      Log On

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Question 456455: If the perimeter of a certain rectangle is 78cm. and the width is 12cm., what is the length?
P=2w + 2l
So, my equation looks like this: 78 = 12w + 2l (I'm not even sure that's right)
This is what I came up with:
I am trying to isolate L.....
78 = 12w + 2l
---------------
2 2
At this point I get confused as to what to do next.....please help?

Found 3 solutions by richwmiller, josmiceli, zeti68:
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
78=2*12+2l
78=24+2l
54=2l
l=27
check
2*12+2*27=78
24+54=78
ok

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+P+=+2w+%2B+2l+
You might want to write it as:
+P+=+w+%2B+w+%2B+l+%2B+l+
given:
+P+=+78+ cm
+w+=+12+ cm
Substituting:
+78+=+12+%2B+12+%2B+l+%2B+l+
+78+=+24+%2B+2l+
Subtract +24+ from both sides
+54+=+2l+
+l+=+27+
The length is 27 cm

Answer by zeti68(10) About Me  (Show Source):
You can put this solution on YOUR website!
Hi,
P=2w + 2L
78 = 2(12) + 2L
78=24+2L
78-24=2L
54=2L
54/2=L
L=27
Answer
length=27cm