SOLUTION: A rectangle that is 90cm and the length and width is unknown, also it is 3cm's longer than twice the width? The perimeter is 90cm's.Need to know the algerbric equasion for this and

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: A rectangle that is 90cm and the length and width is unknown, also it is 3cm's longer than twice the width? The perimeter is 90cm's.Need to know the algerbric equasion for this and      Log On


   

Question 460014: A rectangle that is 90cm and the length and width is unknown, also it is 3cm's longer than twice the width? The perimeter is 90cm's.Need to know the algerbric equasion for this and find the unknowns?
Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
Always list what you know first.
p = perimeter
l = length
w = width
p = 2l + 2w
p = 2(l+w)
p = 90
.
The given relationship has to be turned from English into algebra.
.
length is 3 cm longer than twice the width
l = 2w + 3
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Substitute and solve for l.
.
p = 2l + 2w
p = 2(2w+3) + 2w
p = 4w + 6 + 2w
90 = 6w + 6
84 = 6w
6w = 84
w = 84/6
w = 14 cm
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Substitute this value to find l.
.
l = 2*w + 3
l = 2*14 + 3
l = 31 cm
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Check the perimeter using
l = 31
w = 14
2(31)+2(14) = ??
62 + 28 = 90
Right.
.
Done