Praxis Core Prep: How to Interpret Numeration and Place Values
You will see questions about the number line on the Praxis Core. The numbers represented by points on the number line are coordinates. The points are named not only by their coordinates, but also sometimes by letters that appear above the points. The coordinate of Point C could be 4, for example. The point can also be called 4.
Questions on the Praxis Core exam may go beyond identifying points by the numbers under them. Questions can involve distances, and those questions are rooted in placements of coordinates.
Point C is not labeled, but it is halfway between Points A and D. What is the distance from Point C to Point D?

(A) 4

(B) 3

(C) 5

(D) 2

(E) 7
The correct answer is Choice (A). Since the coordinate of point A is –1 and the coordinate of point D is 7, the distance between them is 8. Half of that distance is 4, and 3 is 4 units from both –1 and 7. Choice (B) is the coordinate of Point C.
Choice (C) is the coordinate of the point that is halfway between Points C and D. Choice (D) is the distance from one labeled coordinate to the next, and Choice (E) is merely the coordinate of Point D.
The number that’s halfway between two numbers is the average of the two numbers. Recall that the average of a group of numbers is the sum of the numbers divided by the number of numbers in the group.