Reflection: Checks for Understanding Let's Review - Section 1: Let's Review Adding More Than 2 Numbers


As I watch students working to add 3 and 4 2-digit numbers, I often find half understandings and misconceptions. I notice that when they add the tens and ones in a problem (such as 15 + 26 + 14 + 35=), they begin by adding 5 + 5 and 6 + 4 to get 10 + 10 = 20. But then they add 1 + 2 + 1 + 3 and get 7, so they add 10 + 7 and get 17 for an answer. They do not look back at the original numbers to see that 17 cannot possibly be the number. They are adding the tens and then adding the ones. The piece that they are still confused about is that the 7 represents 7 tens or 70. 

This is a half understanding, where they know that tens and ones are separate, but by the end of the problem, they have forgotten that the 7 represents 7 tens so they add it in as ones. 

My job here is to reinforce what the digit in the tens place represents. I can do this with base ten blocks, with drawings, and also by having the children count the tens on the number line so they would add 10 + 20 + 10 + 30 and see that they have landed at 70. 

Students at this age need the visual representation of the value of tens and ones to help clear up the misconception/half understanding that they are working with as they try to solve problems.

  Misconceptions and Half Understandings
  Checks for Understanding: Misconceptions and Half Understandings
Loading resource...

Let's Review

Unit 8: Numbers Have Patterns
Lesson 11 of 14

Objective: SWBAT explain the strategies they are using to complete addition and subtraction problems with 2-digit numbers.

Big Idea: Revisit, Revisit, Revisit! Students need repeated exposure to math concepts to really understand how they work.

  Print Lesson
Add this lesson to your favorites
Math, Number Sense and Operations, Algebra, Patterns (Algebra), Place Value, subtraction, addition, place value strategies
  70 minutes
100 1104
Similar Lessons
A Grinchy Christmas
1st Grade Math » Properties of Addition and Subtraction
Big Idea: This Grinch inspired lesson pushes 1st graders to attempt 2 part story problems. It also is a great way to introduce the topic in 2nd grade!
New Orleans, LA
Environment: Urban
Amanda Cole
The Recipe for a Great Word Problem
2nd Grade Math » Addition and Subtraction Basic Training
Big Idea: The big idea of this lesson is to have students write their own word problems to help them have a better understanding of mathematical operations, as they relate to real world scenarios.
Pepperell, MA
Environment: Rural
Kristen O'Connor
What's Your Story?
2nd Grade Math » Working With Numbers!
Big Idea: In this lesson, students will solve and explain more difficult story problems. Additionally, students will explain their thinking in written form.
Jackson, MS
Environment: Urban
Carol Redfield
Something went wrong. See details for more info
Nothing to upload