SOLUTION: I am not sure how to do this type of problem :( The perimeter of a rectangle is 84 ft. the ratio of the width to the length is 2:5. Find the length and the width

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Question 178025This question is from textbook Geometry
: I am not sure how to do this type of problem :( The perimeter of a rectangle is 84 ft. the ratio of the width to the length is 2:5. Find the length and the width This question is from textbook Geometry

Found 2 solutions by HyperBrain, josmiceli:
Answer by HyperBrain(694) About Me  (Show Source):
You can put this solution on YOUR website!
Let x=length
y=width
The perimeter of a rectangle is 84 ft. So,

2(x+y)=84
x+y=42

the ratio of the width to the length is 2:5 so

y%2Fx=2%2F5
5y=2x
y=2x/5

Substituting this to x+y=42,

x+(2x/5)=42
(5x/5)+(2x/5)=42
7x/5=42
x/5=6
x=6*5=30>>length
x+y=42
y+30=42
y=42-30=12>>width

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Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let p= perimeter
Let w= width
Let l= length
p+=+2w+%2B+2l
given:
p+=+84 ft
w%2Fl+=+2%2F5
multiply both sides by 5%2Al
5w+=+2l
w+=+%282%2F5%29%2Al
p+=+2%2A%282%2F5%29%2Al+%2B+2l
84+=+%284%2F5%29%2Al+%2B+2l
Multiply both sides by 5
420+=+4l+%2B+10l
14l+=+420
l+=+30
w+=+%282%2F5%29%2Al
w+=+%282%2F5%29%2A30
w+=+12
The length is 30 ft and the width is 12 ft
check:
p+=+2w+%2B+2l
p+=+2%2A12+%2B+2%2A30
p+=+24+%2B+60
p+=+84
OK