Subtracting with Base 10 Blocks
Subtraction by Adding
This page will provide resources for you to use at home.
Sometimes the information will be posted here or there will be a link to a document.
The document links will direct you to Google Docs. You may download and print these files at your convenience.
If you need clarification about how to use these resources at home,
please contact Ms. Price at her email: rprice@mesquiteisd.org
(click the link above)
Fact Pack
About Learning
the Facts - Addition and Subtraction
Learning
the basic facts is not an end in itself.
The goal is to develop fact fluency so that students can solve problems.
Of
course, our goal is for all of the students to know all of the facts.
Students learn the facts in progressive stages.
Stages in
Learning the Facts
1. Concept
development: Through work with
manipulative materials and problem solving experiences, students come to
understand the meaning of a given number.
For example, to develop the concept of five students find that five can be broken into 1 and 4, 2 and 3,
or 5 and 0.
Fluency
with taking apart numbers to ten and putting them together is an important
skill for developing concepts of larger numbers and learning the basic facts.
2. Strategies: Students employ strategies to find the
answers to basic fact problems.
Although there are 100 basic facts, it is very important for students to
understand that the commutative property cuts the job in half. Turn-around facts, such as 3+7 and 7+3,
use the commutative property.
Beyond that, knowing that adding or
subtracting zero does not change the value of a number, knowing how to quickly
count up one or two, learning the doubles and the strategy for near doubles,
and knowing how to use the make-a-ten strategy account for all but six of the
basic addition facts.
3. Learning
the facts: In the process of
developing number concepts and fact strategies, students come to learn the
basic facts. That is, they no
longer need to think about a fact, they just know it. For example, students may begin by counting up to find the
sum of 8+2, but with experience they no longer need to count up, they
automatically think 8+2=10.
4. Memorizing
the facts: Now is the time to
drill for fluency. Drilling
prematurely simply promotes inefficient strategies and possibly even fear of
arithmetic.
What about timed practice?
Timed practice to build fluency may be effective with some students who
have already learned their basic facts and who enjoy the challenge of the
task. They can learn to recall
facts faster. Timed practice tests have negative effects if students are not
yet using efficient strategies or if they are fearful of the test. In that case, timed practice reinforces
inefficient practices and develops a poor attitude. Because of the potential pitfalls, timed practice tests are
not recommended.
Addition Strategies
The
materials in this Fact Pack are organized to develop fact strategies commonly
employed by students.
·
Facts with Zero: Any number plus zero is
that number. (This is called the
identity property for addition.)
Facts with
zero: 1+0, 2+0, 3+0 …
·
Count Up: When one addend is 1 or
2, it is efficient to count up to find the answer. For example, to add 8+2, the student can count up: 8, 9,
10.
Count
up 1: 3+1, 7+1 …
Count
up 2: 4+2, 9+2 …
(Some
students may use count up for facts with an addend of 3.)
·
Doubles: For some reason, doubles
are quickly learned by students.
Doubles: 2+2, 3+3, 4+4 …
Source: YouTube; Harry Kindergarten Music
·
Neighbors (near doubles): When
the addends are one apart, the near doubles, or “neighbors” strategy can be
used. For example, to remember
7+8, the student can think 7+7 and 1 more, or 8+8 and 1 less.
Neighbors: 3+4, 4+5, 5+6, 6+7, 7+8, 8+9
·
Fast Nines and Fast Eights: When
one of the addends is close to ten (8 or 9), the other addend can be mentally
broken apart to make a ten. For
example, to add 9+7, the student can think 9+1+6; the 7 is broken apart into a
1 -- which goes with the 9 to make 10 -- and 6.
Fast
Nines: 9+3,
9+4, 9+5 …
Fast
Eights: 8+3,
8+4, 8+5 …
This strategy of making a ten can be
used with sevens and other addends, too.
To use the strategy efficiently, it is critical that the student be
fluent with the facts which add to ten:
1+9, 2+8, 3+7, 4+6, 5+5.
·
The Last Six Facts: After becoming fluent
with the strategies above, there are only six facts left to learn.
The
last six facts: 3+5, 3+6, 3+7,
4+6, 4+7, 5+7
Subtraction Strategies
As
with addition, some subtraction facts are more easily learned and then
memorized than others. For
example, subtracting 0, 1 or 2 is easy for most students (such as 9-0, 6-1,
7-2). Also, facts with a
difference of 1 or 2 are easy (such as 9-8, 7-5).
Students
who have a thorough knowledge of addition and an understanding of how addition
and subtraction are related can learn and remember basic subtraction facts
through fact families.
Think
addition: The student uses addition
facts to recall subtraction facts.
Think
addition: 9 – 4 =?
What
do I add to 4 to get 9? or,
4 plus what equals 9?
This
Fact Pack uses fact families and the think addition strategy to help students
learn the basic subtraction facts.
Learning and memorizing the subtraction facts requires the same
intentional teaching and practice as the addition facts.
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