SOLUTION: Hi I need help with problem. I keep getting an impossible answer and i can't figure out what I'm doing wrong. This is the problem: The three sides of an equilateral triangle are in

Algebra ->  Inequalities -> SOLUTION: Hi I need help with problem. I keep getting an impossible answer and i can't figure out what I'm doing wrong. This is the problem: The three sides of an equilateral triangle are in      Log On


   



Question 780019: Hi I need help with problem. I keep getting an impossible answer and i can't figure out what I'm doing wrong. This is the problem: The three sides of an equilateral triangle are increase by 20 cm, 30 cm, and 40 cm, respectively. The perimeter of the resulting triangle is between twice and three times the perimeter of the original triangle. What can you conclude about the length of a side of the original triangle?
Found 2 solutions by stanbon, MathLover1:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The three sides of an equilateral triangle are increase by 20 cm, 30 cm, and 40 cm, respectively. The perimeter of the resulting triangle is between twice and three times the perimeter of the original triangle. What can you conclude about the length of a side of the original triangle?
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Let each side of the equilatera triangle be "x".
New sides are x+20, x+30, and x+40.
New perimeter is 3x+90
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Inequality:
2(3x) < 3x+90 < 3(3x)
6x < 3x+90 < 9x
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3x < 90 < 6x
x < 30 < 2x
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Each side of the orignal triangle is less than 30
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Cheers,
Stan H.
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Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

let the length of a side of the original triangle be x
Perimeter=3x
So new sides are x%2B20,x%2B30,x%2B40, and
Perimeter=3x%2B90
The perimeter of the resulting triangle is between twice and three times the perimeter of the original triangle, or 2%283x%29=+3x%2B90 and 3%283x%29=3x%2B90
So 2%283x%29%3C=3x%2B90%3C=3%283x%29
6x%3C=3x%2B90%3C=9x
3x%3C=90%3C=6x
so x%3C=30 and x%3E=15
So the side lengths of the original triangle are between 15cm and 30cm, or 15cm%3C=x%3C=30cm.