By using the triangle inequality, we conclude that the possible length of the third side is 5ft < x < 17ft.
For a triangle of sides A, B, and C, the triangle inequality says that the sum of any two sides is larger than the other side, so we have:
A + B > C
A + C > B
C + B > A
In this case, two sides measure 6ft and 11ft, and the missing side measures x.
Then we will have:
6ft + 11ft > x
x + 6ft > 11ft
x + 11ft > 6ft
From the first inequality we get the upper bound:
6ft +11 ft > x
17ft > x.
Now, using the second we get:
x + 6ft > 11ft
x > 11ft - 6ft
x > 5ft
(We don't use the last inequality because it will say that x must be larger than a negative number, and the above inequality is more restrictive than that).
Then, if we use the two inequalities that we got we have:
5ft < x < 17ft
The possible length of the third side is 5ft < x < 17ft.
If you want to learn more about triangles, you can read:
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