Multiplication and Division
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Transcript of Multiplication and Division
Multiplication and Division
Math Content – Part 3March 4, 2013
Afternoon Meeting
Welcome Outstanding Coaches,Please greet at least three other people in the room and share why you what you want to know about multiplication and division.
Activity: Form a circle. “I Have… Who Has…..
From, Erny
The Devil’s Library
Learning
We are learning to…Understand how the CCSSM views the
development of multiplicative thinking.Apply strategies that promoting fluency with
single-digit multiplication and division.We will be successful when…
We can help students apply properties of operations as strategies to multiply.
What is Multiplication?Respond in writing in your notebook…
What is multiplication?
Check with a neighbor to see: How is your thinking similar? How is your choice of language similar
or different?
Repeated Addition
Repeated Addition
Begin multiplication instruction with problems involving repeated addition and introduce symbolic multiplication as a shortcut for representing repeated addition problems. Children can be encouraged to first represent repeated addition as an addition expression and then devise a shorthand for such symbolic expressions.
- Baroody, 1998
Strategies- Creatures
Standards…
Read and Reflect on Standards 3.OA: 1 – 6
Share with your shoulder partner a few ideas that struck you as critical to developing a sound understanding of multiplication and division.
From Counting by Ones to Thinking In Groups
Place a large amount of counters in the middle of the table.
On the word “go” grab as many groups of two that you can before we say stop.
Don’t count the total number of sets, just concentrate on making groups of two.
Return the counters to the middle of the table.
On the word “go” grab as many sets of ___3____ that you can before we say stop.
Making groups: What did you notice?
What kind of thinking were you doing as you were making groups?
What would this activity tell you about students’ thinking?
You were just unitizing!(To make or transform into a single unit)
Dot Images
How many dots so you see?
How do you see It?
Draw what you see in your notebook.
Image 1
Image 2
Image 3
Grounding thinking in CCSSM
3.OA.5: Apply properties of operations as strategies to multiply and divide.CommutativeAssociativeDistributive
With your shoulder partner, use an
example, remind each other how these “rules of numbers work.”
Reflect back on 3.OA.5.
Think about how the images were described. Where do the properties show up in the reasoning?
Individually:Quickly glance at the dot image and
determine the number of dots.Jot down using “language” how you saw it.Write an equation that matches your image
and your description.Identify the property or properties you used.
Turn and share.
Image 4
Image 5
Image 6
Revisit Standard 3.OA.5 and 3.OA.7 Take turns with a Shoulder Partner to summarize:
Reflecting on our “dot image” work, what are the main messages of these standards?
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
Examine your word problem:What does the 4 mean?What does the 7 mean?
4 x 7 = ☐
Pose a word problem for:
Number of Groups
Group Size
The total number of objects in 4 groups of 7 objects each.
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
Examine your word problem:What is unknown in your problem:
Number of groups?Group size?
28 ÷ 4 = ☐
Pose a word problem for:
Tell a different story for 28 ÷ 4 = ☐.
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
28 ÷ 4 = ☐
TotalNumber of shares
or Number of objectsin each shareDivision means to partition
to find the number of shares or find the amount in each share.
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
4OA1Interpret a multiplication equation as a comparison, e.g., interpret 35 = 5 x 7 as a statement that 35 is 5 times as many as 7 and 7 times as many as 5. Represent verbal statements of multiplicative comparisons as multiplication equations.
4OA2 Multiply or divide to solve word problems involving multiplicative comparison, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem, distinguishing multiplicative comparison from additive comparison.
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
What’s the new thinking being developed in 40A1 & 2?
“This one is 32 feet higher than that one” 40 feet high, the other 8 feet high
Students in earlier grades learned to compare quantities additively….
Students in Grade 4 learn to compare these quantities multiplicatively…..
“This one is 5 times as high as that one.”
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
Experiences with Compare Word Problems
Individually pose compare word problems for:
6 x 9 = ☐54 ÷ 6 = ☐ with Group Size Unknown54 ÷ 6 = ☐ with Number of Groups
Unknown
When you have a draft of each, turn and check-in with a partner.
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
Connie has 8 times as much money as Melissa. Connie has $56. How much money does Melissa have?
7 x 8 = ☐ Total Unknown
56 ÷ 8 = ☐ Group Size Unknown
56 ÷ 8 = ☐ Number of Groups Unknown
Unknown: Group Size
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
Building Blocks of Algebra
Understand problem situationsRepresent the situation with
objects or diagramsRepresent quantitative relationships
with equationsUse properties of operations as the
basis for strategies
p.13 OA Progressions
Common Core Leadership in Mathematics Project, University of Wisconsin-Milwaukee, Summer Institute 2011
Expanding View of Multiplication
Grade 3: Equal groups--discrete objects, arrays….
Grade 4: Comparison situations--continuous quantities
Grade 5: Stretches or Shrinks (scale factor)
--Context for reasoning multiplicatively with continuous quantities
Oldest Multiplication Chart
Napier Bones
The lattice algorithm for multiplication has been traced to India, where it was in use before A.D.1100. Many students find this particular multiplication algorithm to be one of their favorites. It helps them keep track of all the partial products without having to write extra zeros – and it helps them practice their multiplication facts
1. Create a grid. Write one factor along the top, one digit per cell.
2. Draw diagonals across the cells.
3.Multiply each digit in the top factor by each digit in the side factor. Record each answer in its own cell, placing the tens digit in the upper half of the cell and the ones digit in the bottom half of the cell.
4. Add along each diagonal and record any regroupings in the next diagonal
06
24
1
8
08
32
24
Write the other factor along the outer right side, one digit per cell.
06
24
1
8
08
32
24
35
15
10
49
21
1
4
Partial Products Algorithm for Multiplication
Calculate 50 X 60
6 7X 5 3
Calculate 50 X 7
3,000 350 180 21
Calculate 3 X 60
Calculate 3 X 7 +Add the results 3,551
To find 67 x 53, think of 67 as 60 + 7 and 53 as 50 + 3. Then multiply each part of one sum by each part of the other, and add the results
Calculate 10 X 20
1 4X 2 3
Calculate 20 X 4
200 80 30 12
Calculate 3 X 10
Calculate 3 X 4 +Add the results 322
Let’s try another one.
Calculate 30 X 70
3 8X 7 9
Calculate 70 X 8
2, 100 560 270 72
Calculate 9 X 30
Calculate 9 X 8 +Add the results
Do this one on your own.
3002
Let’s see if you’re right.
Partial QuotientsA Division Algorithm
The Partial Quotients Algorithm uses a series of “at least, but less than” estimates of how many b’s in a. You might begin with multiples of 10 – they’re easiest.
12 158There are at least ten 12’s in 158 (10 x 12=120), but fewer than twenty. (20 x 12 = 240)
10 – 1st guess
- 12038
Subtract
There are more than three (3 x 12 = 36), but fewer than four (4 x 12 = 48). Record 3 as the next guess
3 – 2nd guess- 362 13
Sum of guesses
Subtract
Since 2 is less than 12, you can stop estimating. The final result is the sum of the guesses (10 + 3 = 13) plus what is left over (remainder of 2 )
Let’s try another one
36 7,891100 – 1st guess
- 3,6004,291
Subtract
100 – 2nd guess
- 3,600
7 219 R7 Sum of guesses
Subtract
69110 – 3rd guess- 360
3319 – 4th guess - 324
Now do this one on your own.
43 8,572100 – 1st guess
- 4,3004272
Subtract
90 – 2nd guess-3870
15199 R 15
Sum of guesses
Subtract
4027 – 3rd guess- 301
1012 – 4th guess - 86