computation strategies

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+23+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 onFor 6+2 =

Start at the largest number and count forwards:6…7,8

So 6+2 = 8

______________________ 6 7 8

Counting BackFor 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 90 0 1 2 3 4 5 6 7 8 91 1 2 3 4 5 6 7 8 9 102 2 3 4 5 6 7 8 9 10 11

3 3 4 5 6 7 8 9 10 11 124 4 5 6 7 8 9 10 11 12 135 5 6 7 8 9 10 11 12 13 146 6 7 8 9 10 11 12 13 14 157 7 8 9 10 11 12 13 14 15 168 8 9 10 11 12 13 14 15 16 179 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 ValuePlace 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 Subtraction828 - 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 + 12

42

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 Division20÷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=1302x 20 160 1200 602 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 Division

http://www.pembinatrails.ca/program/earlyyears/Link%205/Numeracy.html

Manitoba Education and Literacyhttp://

www.edu.gov.mb.ca/k12/parents/index.html

A Star and A Wish

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