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COMPUTATIONSTRATEGIES
Presentation for Parents March 2013
Flexible Thinking
There are many ways to solve problems. The more ways we solve a problem, the deeper our
understanding of the mathematics. When we ask "How would you do that?" or "Can you
show me another way?" we are helping children understand math better.
Encourage children to use what they know to solve problems.
Traditional algorithms involving lining up columns rely heavily on memorizing procedures and can work against developing number sense.
85% of all calculations we do involve mental math.
Addition and Subtraction FactsGrades 1, 2 and 3
Doubles
3+3=6
One MoreOne Less
3+1=43-1=2
Counting on 7+2=
Think 7 8, 9
Counting
back 7-2=
Think 7 6, 5
Zero Property 7-0=7
5+0=5
Students will learn mental mathematics strategies to determine basic addition and related subtraction facts to 18.
Friendly
Numbers
7+3= 6 +4=5+5=
Think Addition
for subtracti
on15-6=6+?=15
Number
families
3+4=77+3=77-4=37-3=4
Commutative
Property
(Flip)3+9=9+3=Making
108+5=8+2+3
=10+3=
Doubles
1+1=2 2+2=4 3+3=6
4+4=8 5+5=10 6+6=12
7+7=14 8+8=16 9+9=18
DOUBLES +1DOUBLES -1
FOR 5+6=THINK 5+5 = 10 SO…. 5+6 = 11
FOR 4+5=THINK 5+5 = 10 SO…. 4+5 = 9
Commutative Property(Flip)
FOR 3+9=THINK 9+3 = 12 SO…. 3+9 = 12
Friendly Number 10
1+9 9+1 2+8 8+2
3+7 7+34+6 6+4
5+5
Make 10
When 1 of the numbers you are adding is 7,8 or 9
Go to 10 And add the rest
For 8+5 Think 8 + 2 + 3
10 + 3 = 13So… 8+5 = 13
Counting on
For 6+2 =Start at the largest number and count
forwards:6…7,8
So 6+2 = 8
______________________ 6 7 8
Counting Back
For 6-2 =Start at the largest number and count
backwards:6…5,4
So 6-2 = 4
___________ 4 5 6
Think Addition for Subtraction
For 12- 5=Think 5 + __ = 12
So 12 – 5 = 7
______________________
5 10 12
Zero Property
Any number + 0 or -0 Remains the same
5+0=59-0=9
Number Families
If I know that 3+4=7
I also know that 4+3=77-4=37-3=4
0,1,2/Doubles/ Near Doubles/Make 10
+ 0 1 2 3 4 5 6 7 8 9
0 0 1 2 3 4 5 6 7 8 9
1 1 2 3 4 5 6 7 8 9 10
2 2 3 4 5 6 7 8 9 10 11
3 3 4 5 6 7 8 9 10 11 12
4 4 5 6 7 8 9 10 11 12 13
5 5 6 7 8 9 10 11 12 13 14
6 6 7 8 9 10 11 12 13 14 15
7 7 8 9 10 11 12 13 14 15 16
8 8 9 10 11 12 13 14 15 16 17
9 9 10 11 12 13 14 15 16 17 18
Computation Strategies for Addition and Subtraction of Large Numbers
Students will use personal strategies to add and subtract numbers in problem solving situations.Blank Number
Lines24+8=
+4 +4__________________24 28 32
Place Value(decomposing
numbers) 24+15=
20+10=30
4+5=9
30+9=39Think Addition for
Subtraction52-23=
23+?=52 +20 +7 +2_____________________23 43 50 52
Place Value(Left to Right)
425+3687008013 795
Place Value
Decomposing Numbers 334 + 419 =
(300 + 400) + (30 + 10) + (4 + 9)
700 + 40 + 13
753
Place Value
Place Value Left to Right 334
+ 419Add the 100s 700Add the 10s 40Add the 1s + 13 753
Blank Number Line
Number Line 334 + 419 =
+300 +30 +1 +3
419 719 749 750 753
Think Addition for Subtraction
828 - 729 = 70+28+1=99
+1 +70 +28
729 730 800 828
Multiplication and Divison FactsGrades 3-6
Use a fact you know:
I know 5x8=40
so… 5x9=45
Visualize Arrays
3x2=6÷3=2
Doubling/
Halving
6x4=think
12x2=
Students will demonstrate and apply different mental mathematical strategies to develop recall of basic multiplication facts to 9 x 9 and related division facts.
Think Multiplication for
Division:20÷5=
Think how many groups of 5 are in
20?Or
5x?=20
Fact familie
s3x4=1
24x3=1
212÷4=
312÷3=
4
Commutative
Property3x9=9x3=
Distributive Property
7x6=(5x6) + (2x6)
Doubling and Halving
Doubling and Halving *halve one number and double the other number
15 x 4 =30 x 2=
So 30 x 2 = 60
Skip Counting from a Known Number
Skip Counting from a Known Number
6 X 7 =I know that 5 X 7 = 35So…6 X 7 = 35 + 7 =
42
Distributive Property
6 X 7(6 X 5 =)+(6 X 2 =)
30 + 1242
Commutative Property
6 X 7=7x6=
Arrays
3x2=2x3=6÷3=26÷2=3
Fact Families
6 X 7=427x6=4242÷6=742÷7=6
Think Multiplication for Division
20÷5=Think how many groups of 5 are in
20?Or 5x?=20
Computation Strategies for Multiplication
Students will demonstrate an understanding of multiplication by using different strategies to determine answers.Distributive
Property: 4 x 86 =
(4 x 80) + (4 x 6) 320 + 24=344
Repeated Addition25x4=
25+25+25+25=
Traditional Algorithm
(Left to Right)
26X 8160+ 12172
62x21=1302
x 20 1
60 1200 60
2 40 2
Repeated Addition
15 x 6 =Add 15 six times 15 + 15 + 15 + 15 + 15 + 15
=
30 + 30 + 30 90
Place Value(Distributive Property)
15 x 6 (10 x 6) + (5 x 6)
60 + 30 =
90x 610 60
5 30
Place Value(Left to Right)
Place Value Left to Right15
x 6 60
+30 90
Computation Strategies for Division
Students will demonstrate an understanding of division by using different strategies to determine answers.Fair Sharing
92 ÷4 = 92
20 20 20 20 3 3 3
3
Algorithm
Division
Place Value
4 136 30 -120 + 4 16 34 -16 0
For More information
Pembina Trails School Divisionhttp://
www.pembinatrails.ca/program/earlyyears/Link%205/Numeracy.html
Manitoba Education and Literacyhttp://
www.edu.gov.mb.ca/k12/parents/index.html
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