Are Your Students Struggling with Ordering Decimals…Try This!

To help 5th graders understand decimals last week, I built this number line using an old roll of fax machine paper.  I measured off a little over two meters and then marked every two centimeters to put another number, so I would have room to write the numbers and for them to actually be seen.  Students don’t usually have much of a problem ordering decimals to the hundredths place because they can visualize pennies and dimes, but past that students struggle.  Also, thousandths are a bit daunting to teach…after all they don’t make “thousandths” manipulatives….at least that I am aware of.  This coming week, students are going to build their own number line between two hundredths and we are going to connect all of the number lines and put them somewhere…I am not sure where because it will be VERY LONG because 100 numbers are written on it.  Another something I did to the number line is I glued hundredths blocks down underneath the hundredths numbers, so students could see the concrete representation of these.

 

In case you aren’t familiar in decimal base ten block world:

a flat = 1 whole

a rod = 1 tenth

a unit= 1 hundredth

When explaining hundredths and thousandths to students I do the unthinkable.  I take a blue foam base tenth block and a pair of scissors in front of the class and SNIP a hundredth goes flying a few feet away.  This grabs students attention because #1, I just cut a holy math manipulative, and #2 something just went flying across the room for those students who may have just momentarily zoned out .  No worries, I have had tubs and tubs of these math manipulatives (oh we are calling them “tools” now) that I could build a shrine to them with lit candles.  In other words I have plenty that if I cut one it isn’t a big deal.  THEN, I take the itty bitty hundredth that I just cut and SNIP another slice goes flying.  I tell students that this slice is one thousandth.  This visual really helps students to see how tenths, hundredths, and thousandths are related.  A speck can even be cut off of the thousandth so that students can see what a ten thousandth looks like.  After I have cut all of these pieces off, I put them underneath the document camera so students can see them up close.

Update 4-11-2019 Since this post has become so popular, I am going to list the number line I made that is like the base ten block one above , but it is all nice and printable.