SOLUTION: In a rectangle, the ratio of the width to length is 3:4. If the perimeter is 42. What is the width of the rectangle?

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Question 511760: In a rectangle, the ratio of the width to length is 3:4. If the perimeter is 42. What is the width of the rectangle?
Answer by Maths68(1474) About Me  (Show Source):
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P=42
w:l=3:4
w/l=3/4
w=3/4(l)=3l/4.......(1)
Perimeter = 2 length + 2 width
P=2l+2w
Put the value of p and w in above equation
42=2l+2(3l/4)
42=2l+3l/2
Multiply by 2 both sides
42*2=21*2+2*3l/2
84=4l+3l
84=7l
84/7=l
12=l
l=12
Put the value of l in (1)
w=3l/4=3*12/4=3*3=9
w=9
Perimeter = 42
Length=12
Width=9