The Midpoint Formula
On the number line, suppose point A has coordinate 17 and point B has coordinate 25. What is the coordinate of the midpoint of segment AB?
You can see from the diagram that the coordinate is 21. A shortcut (if you don't want to draw part of a number line) is to find the average of the coordinates:
In 2 dimensions, the coordinates of the midpoint of two points is the average of their coordinates. For example, if the coordinates of A are (2, 3) and the coordinates of B are (10, 11), then the coordinates of the midpoint M of segment AB are (6, 7).
In general, if the points have coordinates (x1, y1) and (x2, y2), then the midpoint M has coordinates that are the average of these:
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Date last modified: October 14, 2008.