Therefore, an algebraic measure is a number with a sign. The sign indicates the direction in which the displacement occurs; a positive sign indicates a displacement from A to B and a negative sign indicates a displacement from B to A.

### Examples

Consider the points *A* and *B* on a directed line.

- The algebraic measure of the set of two points (
*A*,*B*) is the real number*k*such that m(A, B) = \(k \overrightarrow {u}\), where \(\overrightarrow {u}\) is a unit vector. - If m(A, B) = 10, then m(B, A) = −10.

The ratio \(\frac{5}{3}\) of a dilation *D* with a centre *O* is the ratio of two algebraic measures.