Question

what is the disadvantage in comparing line segments by mere observation​

Answer 1

Step-by-step explanation:

When we compare two line segments of almost the same lengths, we cannot be sure about the line segment of greater length. ... Therefore, it is not an appropriate method to compare line segments having a slight difference between their lengths.

Answer 2

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On comparing the lengths of line segments by mere observation the difference may not be obvious for all the pairs of line segments.