Addition and Subtraction Update #2:

The students bring rich math strategies with them to grade three. Most of the strategies we generate come from the student’s ways of thinking about numbers. This is good because it often helps them see that they already have good ways of working with numbers. Some of our best thinkers don’t believe they are good at math. Helping kids use and refine their own strategies is the best way we can help them become more confident and value their own thinking.

Estimating Sums: We use the following three strategies to help us build mental math skills. We focus on learning the strategies and practice deciding which strategies gives the best estimate based on the numbers presented in the problem. I can understand that some people may have a glance at the examples below and feel that it seems a bit silly to estimate. I can reassure you that it is worth the short time we spend on it. Many of the mental math strategies people use resemble some of these estimation strategies. For students who are having a tougher time breaking apart numbers and reconstruct them in their mind, estimation is a good first step. It helps them find an easy way to “get close” to the sum or difference and learn to clean up the left over bits later. Students who already have favorite mental math strategies often discover new ones as we discuss estimation. Once they have a few strategies to work with, they can begin learning to choose the most efficient strategies to use depending on the numbers presented in the problem. In short, we have very rich conversations and great thinking springs from our simple estimation strategies.

1. Add only the digits in the tens place.

59+23
50+20=70
So, 59+23 is estimated to be 70.

2. Take one number to the closest 10.

59+23
60+23=73
So, 59+23 is estimated to be 73.

3. Take both numbers to the closest 10.

59+23
60+20=80
So, 59+23 is estimated to be 80.

 

Estimating Differences:

1.Take each number to the nearest 10.

59-23
60-20=40
So, 59-23 is estimated to be 40.

2. Subtract only the numbers in the 10’s place.
59-23
50-20=30
So, 59-23 is estimated to be 30.

3.Use only the 10’s from the number being subtracted.
59-23
59-20=39
So, 59-23 is estimated to be 39.

Adding Two Digit Numbers:

1.  Add the tens, then the ones to the first addend. (This

45+37
45+30=75
75+7=82

2. Add the tens together, add the ones together, then add up their totals

45+37
40+30=70
5+7=12
70+12=82

2. Use a number line to count on or count back.
45+37=

45—–55—–65—–75—–82  (Skip count on by 10’s, then add the 7)

Subtracting Two Digit Numbers:

1. Subtract the tens of the minuend, then the ones.
45-37
45-30=15
15-7=8

2. Use a number line to count on or count back.

45—–35—–25—–15—–8 (skip count back by 10’s, then count back 8 more)

The examples above a just a small taste of the many ways your children know how to work with numbers. I look forward to sharing more with you in future posts.

Spelling Practice:

The students are going to bring home a list of words to practice. Their first list will be sent home in the next couple of days. The list will be made up of words they did not know how to spell when they were completing writing projects. Please help them practice their list until they know how to spell the words. There will be no spelling test at school. Doing a spelling test for each student just isn’t practical. Plus, the practice is far more important than the test.

How do the kids create their lists? The process is quite simple. When completing writing assignments big or small, the students know to circle any word they are not sure about. Later, they use the dictionary app on the iPads or chrome books to find out how to spell the words correctly. These are the words they add to their spelling list. Kids often get hung up on the spelling of a word, which can get in the way of getting their thoughts down on paper. This way, they don’t have to worry about it while they write because they know it will be taken care of later.

 

Thanks for your help!

Addition and Subtraction Unit Update #1:

Here is a quick overview of what we have been practicing so far in our Addition and Subtraction unit.  We are working with 2 and three digit numbers now, but these are some of the important single digit strategies that we have reviewed. I will post more about some of the other strategies we have been working with soon!

1. Doubles and Near-Doubles Addition Facts:   We spent quite a bit of time practicing our doubles facts as a class and individually.  We focus on doubles because they are often easy to learn and can be a helpful mental math strategy for solving other addition facts that are close to the double. Students practiced solving “near doubles” equations and explaining the strategy as clearly as they can.

Example:
6+8=?
I know 6+6=12
6+8 is 2 more.
So, 6+8=14

or

I know 8+8=16
6+8 is 2 less.
So, 6+8=14

2. Making 10:
Example: To solve 6+8  we may think: Take 2 from the 6, leaving 4.  Add 2 to the 8 to make 10, then add the 4 to get 14.

Or, use an adding a 10 fact like the example below.

We know 10+6=16.
8+6 is 2 less.
So, 8+6=14.

We have also been practicing our addition facts that make 10.

3. Related Addition and Subtraction Facts (Fact Families):
Example: If we know 7+6=13 we also know 6+7=13, 13-6=7, 13-7=6.  Using “fact family” knowledge is often most useful for students to solve subtraction equations by thinking of the related addition fact.

Addition and Subtraction

Our class started a mathematics unit on addition and subtraction.  Your child will develop strategies for adding and subtracting whole numbers by using addition charts, mental math, estimation, Base Ten Blocks, place-value mats, and pencil and paper.

In this unit, your child will:

  • Recall basic addition and subtraction facts
  • Identify and apply relationships between addition and subtraction
  • Add and subtract 2-digit numbers
  • Use mental math to add and subtract
  • Estimate sums and differences
  • Add and subtract 3-digit numbers

The ability to use a variety of strategies to add and subtract leads to the development of a strong sense of number.  I will post the strategies that we are learning as we move through the unit.

Learning Teams:

We work together in a variety of ways. Today, the students are in learning teams. They will spend the day supporting each other as they work on math skills, create writing projects, read, and think about communities in social studies.  The teams are responsible for choosing when (and sometimes how) they accomplish each job. That means there are many subjects and activities being explored at the same time in our classroom. When the kids have completed the jobs outlined for the day, they have many other learning choices they can explore. Sound like Chaos?? Believe it or not, it isn’t. Your children manage these moments very well. They are great at taking responsibility for their learning.

Important Dates in December:

Monday, December 2
– See a Need, Fill a Need campaign begins and ends on Dec. 11

Wednesday, December 4
–  December Scholastic book orders are due
– In the morning, Grade 3s are walking to WHS to see a production of The Little Mermaid

Thursday, December 12
– Christmas Family Festival 6:30 pm – 7:30 pm
– SRC Christmas Bake Sale 12:00 pm – 1:00 pm

Tuesday, December 17
-SCC Pizza Hut Hot Lunch

Friday, December 20
– SRC Christmas Sweater Spirit Day

Monday, December 23
– Christmas break begins

Monday, January 6
– Classes resume