Lesson 35:  Intro to Number Line Problems

This lesson involves a variant of thermometer and bar graph problems.  It's important to understand how to identify points on a number line which does not have every tick-mark labeled.  This lesson will show you how. 

Don't forget to watch the embedded video clip for this lesson at the bottom of the page.  Please be sure to read the embedded video information and disclaimer.

Take a look at the two number lines below.  In each one, we need to identify the numbers that are represented by two different points.  We have to use some basic math, and some basic deductive reasoning. 

First we have to figure out what number each tick mark represents.  Look at the first number line.  It starts with 720, then the next tick mark is not labeled, but the one after that is 740.  That tells that the unlabeled one must represent 730, since it is halfway between the 720 and the 740.  If you were doing this on paper, you could then write in the values of all of the unlabeled tick marks. 

With this knowledge, we can see that Point B is at 770, but finding Point A involves an extra step.  Point A is halfway between 740, and what we figured out is 750.  That means that it represents 745, which is halfway between those two numbers. 

Look at the second number line.  Here you can see that each tick mark represents 4, using the same logic as above.  First we can fill in the values of the missing tick marks, counting by fours.  We can then easily see that Point D is at 44.  Point C is halfway between 36 and 40, so we know that it is 38.

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