Question

Find the length of the third side. If necessary, round to the nearest tenth.
4 , 5 and x . whats the third side?

Answer 1

If 4, 5 and x are the side lengths of a triangle, the triangle inequality gives
|5 − 4| < x < 5 + 4,
so 1 < x < 9. (If degenerate triangles are allowed then 1 ≤ x ≤ 9.) No rounding is necessary.