teaching fractions - the learning exchange · fractions is treated as a discrete topic “fractions...
TRANSCRIPT
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Teaching Fractions What’s the big deal? Dr. Cathy Bruce Supported by Shelley Yearley November 2014
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Agenda
§ current research on what makes fractions challenging for students
§ what foundational fractions concepts need more attention
§ which representations are helpful to students
§ key strategies for supporting educators who are teaching fractions
§ Interaction through the chat window, polls and an experiment with a whiteboard
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1. Why is fractions
learning so challenging?
What the research says…
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What we know from research
§ Fractions is treated as a discrete topic
“fractions unit” tends to be taught in isolation from other math content
Even though fractions is inherent in much of the mathematics … “I’m teaching measurement now, I am not doing fractions”
….
Persistence with whole number counting and contexts in school math does not help…
Problem 1
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Continuous vs Whole number thinking § We rote count 1,2,3,4….
§ We don’t count one, one and one-half, two, two and one-half… etc. Unless we are really stalling
§ We focus on whole numbers all through primary (and junior) grades, and then switch to the continuous number system hoping students will transfer the concepts
§ Two problems: a. continuous and whole number thinking are very
different; b. we have lost the child’s intuitive understandings of
rational numbers
Problem 2
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Understanding Density
Tirosh, Fischbein, Graeber, & Wilson (1998) Only 24 % [of 4th and 5th graders] knew that there was an infinite amount of numbers between any two numbers
43 % claimed that there are no numbers between _ and _
Based upon research by Dr. Cathy Bruce, Trent University and Curriculum and Assessment Policy Branch
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Think of a metaphor…
§ What might you use as a metaphor to describe the density of the number line – say between 1 and 2?
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More challenges…
§ We conflate the meanings of fractions and their representations
Set model Part-whole fractions thinking (not part-part) Could we think about this as part-part?
Problem 3
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§ Multitude of representations in North American textbooks
§ Circular area models are overrepresented and pose difficulties (difficult to equi-partition, precedes introduction of deep study the circle)
Problem 4
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Students attempting to partition…Partitioning Circles
HMMMM……
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Multiple Meanings of Fractions
§ Linear measure (a distance from 0 in either direction)
§ Part-whole relationship (relative quantity, often area-based, but can also be set-based)
§ Part-part relationship (ratios)
§ Fraction as operator (multiplicative action on quantity)
§ Fraction as quotient (division relationship)
A fraction is one quantity or amount
Problem 5
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Ways we think
about fractions
www.edugains.ca Or go from: tmerc.ca (fractions tab)
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Part-whole Relationships
0 1 2 26
Linear models
2D Area models
3D models (volume; surface area)
26
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Part-whole Set Relationships 26
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Part-part Relationships § 2 parts orange concentrate to
6 parts water
§ 2:6
26
Put another part-part ratio example into the chat space now
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The Research is Clear Mooseley’s 2005 research :
§ demonstrated that students who were familiar with both the part-part and part-whole interpretations had a deeper understanding of rational numbers.
§ highlighted the need to expand students’ fractions understanding beyond the typical meaning that is focused on in mathematics programs in North America-fractions as part-whole relationships.
Based upon research by Dr. Cathy Bruce, Trent University in partnership with the Curriculum and Assessment Policy Branch
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Behr, Harel, Post & Lesh (1993) have state that
“…learning fractions is probably one of the most serious obstacles to the mathematical maturation of children.”
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Leads to challenges in work and life…
§ Calculation of dosage errors
§ Measure twice, but still cut 3 times
§ Estimations of time
§ Conservation of liquid
§ Baking
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Fractions Research Team 2011-2014
Tara Flynn
!
!
TRENT MATHEMATICS EDUCATION RESEARCH COLLABORATIVE
DSBN HWDSB KPRDSB OCDSB SCDSB
SMCDSB TLDSB YCDSB
Cathy Bruce
Shelley Yearley Sarah Bennett Rich McPherson
Curriculum and Assessment Policy
Branch
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Collaborative Action Research Process tmerc.ca
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Context and Participants
§ 8 school boards § Kawartha Pine Ridge § Trillium Lakelands § Ottawa Carleton § DSB Niagara
§ 75 classroom teachers
§ 1000+ students (to date)
§ Shortest interval 4 months; longest 8 months
§ Simcoe County § Simcoe Muskoka Catholic § York Catholic § Hamilton Wentworth
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Data Collection
§ STUDENTS § video of student
thinking § written student
responses § clinical interviews § Pre-post tests
Pre- and post-data initally collected using a tool validated by Ross and Bruce (2009), then revised, by Bruce, Flynn & Yearley, field-tested and validated again (design research process)
§ TEACHERS § video of discussion § lessons and
instructional sequences
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Overarching Research Question
What instructional strategies and tools support junior and intermediate grade
students in learning fractions?
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Pre-post Assessment Qs
1. Show five-sixths in two ways. 2. is the same as . How do you know? 3. The sum of and is closest to: a. 20 b. 8 c. d. 1
43
2015
121
87
21
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Year 1 Research Findings: Punctuated Instruction Sample
Data Set
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Year 3: Grade 4 PD Outcomes
Based upon research by Dr. Cathy Bruce, Trent University and one district school board.
0
2
4
6
8
10
12
14
16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Pre Mean Post Mean
All classes Pre: 5.26 Post: 11.14
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Year 3: Pre-post Mean Differences
Board Grades n Pre-Post Mean Difference
d
1 3-6 132 +29.81% 1.23
2 3-9 172 +25.91% 1.07
3 6-8 83 +10.33% .43
Based upon research by Dr. Cathy Bruce, Trent University and Curriculum and Assessment Policy Branch and three DSBs
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Based upon research by Dr. Cathy Bruce, Trent
University and Curriculum and
Assessment Policy Branch and three DSBs
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Based upon research by Dr. Cathy Bruce, Trent University and Curriculum and Assessment Policy Branch Research Product
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Time for some math!
Two-fifths of the marbles are blue and three-tenths of the
marbles are yellow. Are there more blue or yellow marbles in
the bag?
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Does the number line help make sense of this situation? § Using a linear model (Petit, p. 156)
§ of the marbles are blue
§ of the marbles are green
§ Are there more blue or mint green marbles in the bag?
A comparing fractions situation
25310
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2. What foundational
concepts need attention? Unit fractions
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Explicit Instruction of Unit Fractions § Students should have the experience of composing
and decomposing fractions using unit fractions:
e.g.,
e.g., is ‘2 one-fifth units’
§ Use of unit fractions allows students to make connections between the different constructs of numbers and “provides a catalyst for students’ transition from whole to rationale numbers” (Charalambous et al., 2010).
21
41 ,
52
The ‘4’ or the ‘2’ are not the whole, they are the unit we are counting
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Let’s Count
Fifths
1 one-fifth units
2 one-fifths
3 one-fifths
4 one-fifths
5 one-fifths
6 one-fifths
7 one-fifths
Sixths
§ Count aloud by sixths
§ When you reach a whole, say BUZZ instead of the fraction quantity
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Unit Thinking is Powerful Whole Numbers 2 + 3 2 1 units + 3 1 units 5 1 units
= 5 Decimal Numbers 0.2 + 0.3 2 0.1 units + 3 0.1 units 5 0.1 units
= 0.5
Fractions
73
+72
712 units
713 units
715 units
75
=
Algebra 2a + 3a 2 a units + 3 a units 5 a units
= 5a
It allows students to connect their understanding of operations across number systems.
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Which is greater : or How do you know? Which is greater : or How do you know?
Based upon research by Dr. Cathy Bruce, Trent University and Curriculum and Assessment Policy Branch
87
85
123
103
Use Unit Fractions Reasoning
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Student Thinking
Based upon research by Dr. Cathy Bruce, Trent University and Curriculum and Assessment Policy Branch
Parker Comparing Fractions
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Implications
§ Engage students in composing and decomposing fractions using unit fractions
§ Have students name the units, including counting by unit fractions (1 one-fifth, 2 one-fifths, 3 one-fifths, …)
§ Come back to unit fractions regularly – including for operations with fractions
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3. Powerful representations
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We have explored linear, area and set models in detail
Which representation is helpful in which situations?
Tad Watanabe, 2002 TCM article
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Representations
The use of linear (and some area) visual representations, such as:
number lines
bars, strips or ribbons
enable students to think about partitioning and iterating as relative length or distance (or area) relationships, which is a particularly powerful way to make sense of fractional parts.
Math teaching for learning: Developing Proficiency with Partitioning, Iterating, and Disembedding , 2013
Based upon research by Dr. Cathy Bruce, Trent University and Curriculum and Assessment Policy Branch
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Why Number Lines?
§ To further develop understanding of fraction size (PROPORTIONAL REASONING)
§ To see that the interval between two fractions can be
further partitioned (DENSITY) § To see that the same point on the number line
represents an infinite number of equivalent fractions (EQUIVALENCY)
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Circle Rectangle Line Set Symbol # sentence
corr
ect 7 35 26 2 42 31 2
8 26 20 1 26 48
inco
rrec
t 7 16 4 11 17 2
8 8 2 5 18
In all four classrooms students used circles far more frequently than any other continuous representation; difficulty with partitioning into fifths and tenths was evident; in one class the students redrew the circle a number of times and seemed to be attempting to create equivalent sectors but were unclear as to exactly how much accuracy was required and also did not attempt rectangular or set representations. Observations from exploratory lessons, researcher
Circle Rectangle Number line
Set Symbols Words
Equivalence Percent/ decimal
corr
ect Grade 6 6 21 1 5 5 1
Grade 7 3 6 2 2 2
inco
rrec
t Grade 6 11 2 1 1
Grade 7 1 1 1 5 4
Examining Representation Use
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Context
§ Walking to school; three-fifths of the way there
§ Comparing one-fourth of a glass of orange juice to two-sevenths of a glass of grape juice
§ Finding the ratio of red stones to white stones in the basket
§ Adding 4 one-fifths and 6 one-fifths
§ Multiplying one-sixth and one-third
Write in the chat space which representation you think makes
a good fit with the context
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Multiplying one-sixth and one-third
3 columns
6 ro
ws
One-eighteenth of the area model is shaded green
Multiplication can be understood as: • Groups of (set) • Repeated addition
(linear) • Shared space (area)
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4. Helping educators
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Key Strategies
§ Inquiry about fractions: Find a buddy, try tasks together and watch/listen to students
§ Slow it down to speed it up: do one thing well – it will travel
§ Be thoughtful about tasks and representations
§ Use existing resources to support learning—digital paper, lessons, video studies
tmerc.ca & edugains sites
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Q and A
§ We have been monitoring your questions throughout the session.
§ Please ask a key question in the chat space now, and we will try to address that, or at least open up a discussion and some additional thinking.