Friday, 9 September 2016

Making Sense of Rounding

Has anyone else witnessed this look after they have taught their students a lesson on  how to round?

Rounding can be a confusing concept!  There are some cute chants we can teach our students to sing, but is that really teaching them the number sense necessary to master this skill?  I'm not sure...

Here are some simple techniques you can use in your classroom to help teach your students the number sense necessary for rounding.  These ideas are concrete methods that will not only help build number fluency while also teach them how to round.

Using a Number Line to Round
This strategy builds on the the idea that when rounding, if a number is 5 or greater, you round the number to the next ten, hundred, thousand, etc. and if the number is less than 5, the place value stays the same.
For example, lets say we are rounding the number 67 to the nearest 10. Students would create the number line as shown below.

Since 67 is past our halfway point, students know that we round to the next 10 which is 70.

Here is another example for you- Let's say we want to round 543 to the nearest hundred.  Students would create the number line as shown below:

Since 543 comes before our halfway number, we would leave the hundreds place the same, which is 500.
I know, I know, this is a different approach, BUT, try it a few times with your students and you will see they will actually "get" it. 
 Download this  number line template by clicking HERE.  

I also really like to break out our graduated cylinders (also known to my 3rd graders as measuring cylinders).  I set up a few stations by filling the cylinders with different amounts of water.  Students list the amount of water in each cylinder and then round the amount to the nearest 10.  What is the benefit of this? 
1. Students are getting practice in reading liquid measurement.
2.  The visuals on the cylinders are perfect for rounding.  The units on the cylinders count by 10- reinforcing the concept of finding the nearest 10.  Also students can see the halfway point- reinforcing the concept that if the liquid measurement is past the halfway point, we will round to the next 10 and if it is less, we keep the current 10.

And last but not least, how do we keep learning fun? By games of course!  We play Alien Abduction, where students have to find the halfway number (abducted by aliens).  When checking for understanding, students use the "Round to the Next 10 or 100" and "Keep the 10 or 100" the same signs.  I give students a number to round and they show me how they would round the number by showing me the correct side of the sign.  And, to get students up and moving we also do a "'Round the Room" activity where students match numbers placed around the room to rounding clues.
And there you have it!  I hope these strategies help make teaching rounding more understandable and fun for your students.  

Download these FREEBIE activities by clicking HERE.

Clip art from Rebecca B Designs

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