Question 560275
can 7, 8, 18 be a measurment of a triangle 
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Ans: No, because 7+8 is less than 18
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Try it.  Let a line segment be 18
Start a legment of length 7 on one end
and a segment of length 8 on the other end.
Notice that they cannot meet to form a triangle
because 7+8 < 18.
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Cheers,
Stan H.
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