Today we discussed how you would place a decimal number on a number line to help you compare two decimal numbers. I gave the students the number 3.386 and we broke it down to it's smallest pieces.
Next we acted like we were only working with the number 3.3. We discussed the fact that we were working with 10ths, and since our number was .3 larger than 3, we needed to create a number line where our beginning number was 3 and our ending number was 4, since 10th fall between two whole numbers.
This pattern continued.... we worked with 3.38. Our new number line began with 3.3 and ended with 3.4 since hundredths would fall between two tenths numbers.
Finally, we worked with the original number 3.386. At this point the classes were able to tell me that this number would need to be placed between two hundredths numbers on a number line.
The most difficult concept to get across is that you are "zooming" in, or magnifying, a portion of the number line as you work with decimals.
- For example, to "see" 10ths, you have to magnify the whole number section that would contain the 10ths. For our number (3.386), we needed to "zoom in" between the whole number 3 and the whole number 4 to place the number 3.3 on a number line.
- To "see" 100ths you have to magnify the 10ths section. We would "zoom in" between 3.3 and 3.4 in order to plot 3.38 on a number line.
- To "see" 1000ths you have to magnify the 100ths section. We would "zoom in" between 3.38 and 3.39 in order to plot 3.386 on a number line.
The completed page is shown above, but if you would like to see the process, please watch the video at: Decimals on a Number Line.
Once we had completed our number lines, we went to khanacademy.org, searched "Decimals on a Number Line," watched the video, and worked the skill problems. With the remaining time, students continued working on math concepts on khanacademy.org.