Question 166102: A collection of triangles and pentagons contains 40 shapes having a total of 138 sides. How many pentagons are there? Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! A collection of triangles and pentagons contains 40 shapes having a total of 138 sides. How many pentagons are there?
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# of shapes equation: p + t = 40
# of sides equation: 5p +3t = 138
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Multiply thru 1st by 3 to get:
3p + 3t = 120
5p + 3t = 138
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Subtract 1st from 2nd to get:
2p = 18
p = 9 (# of pentagons)
Since p + t = 40, t = 31 (# of triangles)
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Cheers,
Stan H.
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