Rounding Strategies: 3NBT1, 4NBT3, 5NBT4

     After a rough start, my leveled Math class is going smoothly at last.  My students have gotten into a routine of a whole-class lesson on Monday (with pre-test), differentiated instruction based on the pre-test on Tuesday, Wednesday, and Thursday, finishing with another whole-class lesson on Friday with a final, standards-based quiz on that day.  Most students are seeing growth as they graph their pre- and post-assessments.  With this leveled group, I have often found that the class doesn't usually fall into three groups, like I have seen with heterogeneous groups in the past.  Quite often, they only fall into two groups.  This has lead to some changes in my I Love Math groups.  Most of the time, I divide the class into two groups.  One works with me while the other works on their Ten Marks or Manga High assignments on the computer.  Then the switch.  When there is a preponderance of students who have mastered the pre-test, I will often include Wednesday as an additional whole-class lesson. 
     This past week we worked on rounding.  Rounding was one of those skills that no one in the class was even close to mastering, even after the first whole-class lesson.  I had to dig deeper in order to meet my students' needs.
     The first resources I used was Learn Zillion.  Using the Quick Code LZ525 you can see a great lesson that uses a number line to show how to round.  We used the following template:

original number:_____________________

 

 

____________________________________________________________________________________

 

 

__________                                                   __________                                                    __________

low benchmark                                                 midpoint                                                 high benchmark

 

     For each  number, they created an individual number line and place the original number as a dot on that number line.  This was a time consuming process, but after doing several together, the light bulb went on for many struggling students who could finally SEE what it means to round.

     After a differentiation day where I reinforced this method, I taught method number 2.  This I introduced as a "game" I called "Slap! Trap!".  I passed out a place value chart and a highlighter.  (Kids always get excited when the highlighters come out!)  Students used a pencil and the chart to write the number to round. 

  I announced: "Round to the nearest thousands!".  Students repeated: "Thousands, thousands, thousands, slap, TRAP!"  When they say slap, they use their left pointer finger to cover the digit in the given place.

 

 When they say trap, they color the digit in the next place to the right with the highlighter.  If the digit they "trapped" is 5 or more, the digit they "slapped" will go up by one.  If not, it will stay the same. 

 

All the digits to the right of the slapped/rounded digit turn into zeroes.  Any digits to the left of the slapped/rounded digit stay the same.  After the number line method, this seemed like a shortcut to many students.

     After instruction, some students gravitated to one method; some to the other.  In the end, all students benefitted from learning both methods.