Introduction to Geometry: Measuring Segments

Coordinate of a Point and Comparing Numbers Using the Number Line

The number associated with a point on a number line is called the coordinate of the point. For example, the coordinates of M, N, and P, in the figure below are -1.5, -3.25, and 3.5, respectively.

number line with the points negative 4, negative 3, negative 2, negative 1, 0, 1, 2, 3 and 4 labeled, between negative 4 and negative 3, the point N is labeled, between negative 2 and negative 1, the point M is labeled, and between 3 and 4, the point P is labeled

As points are positioned further from the origin to the right, their corresponding numbers increase. For example, in the figure below, the number correspondent to D is greater than the number correspondent to F, because D is further from the origin then F.

number line with the points negative 4, negative 3, negative 2, negative 1, 0, 1, 2, 3 and 4 labeled, between 1 and 2, the point B is labeled and between 3 and 4, the point D is labeled

As points are positioned further from the origin on the left side, their values decrease. For example, in the figure below, the number correspondent to A is less than the number correspondent to M, because A is further away from the origin then M.

number line with the points negative 4, negative 3, negative 2, negative 1, 0, 1, 2, 3 and 4 labeled, between negative 4 and negative 3, the point A is labeled and between negatve 2 and negative 1, the point M is labeled