Oakland Terrace Grades 2 & 3 Math Student Work

Students in Ms. Mervis's and Ms. Lewis's classes explore adding 2 and 3 digit numbers with regrouping. This lesson in the computer lab uses the following online manipulative from the National Library of Math Manipulatives: http://nlvm.usu.edu/en/nav/vm1_asid_154.html.

This lesson was taught to introduce addition with regrouping. The students are given a chance to explore using the online manipulative before they are taught the algorithm.

Online manipulative showing the addition expression: 17 + 74

The student sees the online base ten blocks representing the expression 17 + 74. She then records on her worksheet what she sees on the computer.
Student work showing a visual representation of the base ten blocks for 17 + 74

Student work showing a visual representation of the base ten blocks for 17 + 74

Students see that there are more than 9 ones. So, the ones must be regrouped. By merging ten ones together, the students see that they can make a ten. The students do not need to be introduced to the algorithm yet to see why this works. The students see that the ten that was created must be moved to the tens place.

When the ten is moved, and all of the regrouping has been completed successfully, the computer shows the correct answer. The logic of regrouping the ones to make a ten is clear. In many ways, the online manipulative is better than actually manipulatives. When using actual base ten blocks with larger numbers, students often mix up the blocks and get confused about "trading in" ones for tens.

Online manipulative showing the addition expression: 777 + 26

Students can easily move to adding three digit numbers with regrouping. The algorithm still has not been introduced.
Student work showing a visual representation of the base ten blocks for 777 + 26

Student work showing a visual representation of the base ten blocks for 777 + 26

The ones are regrouped to form another ten.

The ten is moved from the ones place to the tens place.

The 10 tens are regrouped to form another hundred.

The hundred is moved from the tens place to the hundreds place. Because all of the regrouping has been completed, the computer shows the answer.

Now, students have a better conceptual framework to learn the addition with regrouping algorithm.

Download a PDF file of this activity.

Indicators:
6.2.5.1 model two-digit addition and
subtraction using manipulatives.
6.2.5.3 add two- and three-digit
numbers with regrouping.