Wednesday, September 19, 2012

Rounding Whole Numbers

Rounding to the Nearest 10s
(but this activity can be used for most any type of rounding.)
With the two older students, who had not yet been accepted in MVCA, I was doing review to see where the students were at.  So, first off we did a Rounding Notebooking page.  This was a way to introduce the roller coaster/hill effect to rounding with using a number line. 
Then the children began doing some sheets to show me what they knew.  The 3rd grader was definitely not sure about rounding to the 10s place.  So I did the activity below with her.
I drew a hill that looked like her rounding notebook page on the magnetic dry-erase board. Then wrote the poem down that they had written down to go with their notebooking page.
Find the number,
Look right next door,
5 or more?
Raise the score!
4 or less?
Let it rest!
The houses were a twist from what I did with them during our place value review.
 Here it shows one house for each section.  On the board I used a house for each place.
Thousands, hundreds, tens, ones.
Note that I used a red roof for the 10s.  This was to remind her what we were rounding to and help her know what number was "next door".
We actually started with a single digit number and moved our way up to a 4 digit number when she was able to answer correctly and consistently.  For the pictures I used the 4 digit number but I do strongly suggest starting at just one digit, and be sure to use 4 or less and 5 or more digits in the ones place for each number of digits.  :-)  This was awesome for slipping in 'writing' numbers up to 9,999. 
After putting the number you are wanting to round up on the houses, then the next step is to put the number "next door" on the correct side of the hill.  Here we state "5 or more, raise the score; 4 or less, let it rest."

She knew that the last digit of the rounded number will always be zero so she put the zero in its place and then decided that she needed to "raise the score" so she brought down the 5 and put a 6 in it's place.  And then to slip in that extra "reading numbers to 9,999", she read the rounded number to me.
Turned into an easy and excellent, hands-on activity for rounding.  The moving of pieces really helped her understand what we were doing.  So tomorrow...she's going to get another set of numbers to round and be able to use the board if she wants, but I'm looking for her ability to round without the board.

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