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Welcome to my math blog! The purpose of this blog is to help you stay informed about our learning and experiences that have taken place during our math class. I have also included links your child (and you) may want to use in order to supplement math learning in 5th grade.

Thursday, November 13, 2014

Decimals on a Number Line

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.
We began by acting like we were only working with the number 3.  We created a number line and plotted the whole number "3" on it.  This was not a problem, students have been plotting numbers on number lines for years.... but we weren't finished.  We needed to move into plotting decimal numbers on number lines, so to help make the visual, we used colored pencils.  Anytime we were working with a whole number we used red.

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.

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