Answer:
Step-by-step explanation:
Consider the case where each part is of length 1. Then the midpoint of the first segment is at 1/2.
a) If there are 3 segments, the midpoint of the last segment is halfway between 2 and 3, at 2 1/2. The distance from the first midpoint to the last midpoint is ...
... 2 1/2 - 1/2 = 2 . . . . . that is, 2/3 of the total line length
When the line length is m, that is 2/3·m
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b) If there are 5 segments, the midpoint of the last segment is halfway between 4 and 5, at 4 1/2. The distance from the first midpoint to the last midpoint is ...
... 4 1/2 - 1/2 = 4 . . . . . that is, 4/5 of the total line length
When the line length is m, that is 4/5·m