The Ruler Postulate

Read pages 56-57.

The Ruler Postulate is not as complicated as it sounds. Take a ruler:

You can see pretty easily that:

1. A given number corresponds to a certain point. This is called its coordinate.
2. There is never more than one point to a number.
3. If you take any two points on a given ruler, the distance between the two points is given in terms of a real number (say, 20 is the distance between 10 and 30 on the purple ruler).
4. You can express this as a formula |x-y| given that x is 30 and y is 20. This formula can be used whenever you need to know the distance between two points (this is important! HJ will be asking several of this kind of question in the exercises!

EXAMPLE:

If 400 in the first ruler was A and 200 was D, then the distance between the two in terms of letters would be |A-D|. Does that make sense?

DO;

• Set I -- # 10 - 19
• Set II -- #24-31