strategies to support student learning of fractions cynthia santosuosso

STRATEGIES TO SUPPORT STUDENT LEARNING OF FRACTIONS

Cynthia Santosuosso

The Research…

Only 24 % of thirteen and seventeen-year-old students identified 2 as the estimated sum for 12/13 + 7/8, while a greater percentage identified 19 or 21 as the estimated sum.

Only 50% of eight grade students successfully arranged 2/7, 1/12, and 5/9 from least to greatest.

Based on the NAEP (National Assessment of Educational Progress).

Why are fractions so challenging? The way that fractions are written Classroom practices designed to help

students make sense of fraction values mask the meaning of fractions.

Students’ overreliance on whole number knowledge

The many meanings of fractions, such as measure and ratio

Fraction sense

A deep and flexible understanding of fractions that is not dependent on any one context or type of problem

Tied to common sense Allows students to reason about fractions

Fraction Sense

This workshop is based around teaching scenarios.

From each of these scenarios will be drawn: key ideas about fractions

how to communicate these ideas to students

Workshop Format

Ms. Chu reviews some basic fraction concepts with her fifth graders. While examining their work, she notes that the drawings of more successful students varied, depending on the details of the problem. Students who were less successful relied solely on drawing circles (or pizzas), regardless of the problem type or context.

Scenario: Illustrating fractionsGrades Taught: Third, fourth, and fifth

Consider….

What can Ms. Chu do to expand her students’ drawings?

The Math…Area Model

Fractions are based on parts of an area or region

Circles Most common Emphasize amount that is remaining to make up

whole Not as flexible as other area or region because

don’t allow for different-sized units Rectangles Pattern Blocks Paper Folding

The Math…Linear Model

Lengths are compared instead of areas Fraction Strips Cuisenaire Rods Number Line

Important to note that each number on number line denotes the distance of the labeled point from zero, not the point itself

Often difficult for students to view as comparing lengths

The Math…Set Model

Whole is understood to be a set of objects & subsets make up fractional parts

Two color counters often used to model fractional parts

Key Idea

Understanding the relationship between representations of the same idea is core to fraction sense.

Classroom Activities to Support this Idea

Provide students with a fraction (1/10) and have them draw an example of each type of fraction model. For example: One cake shared among ten people (area model

using a rectangle) A pizza divided into ten equal pieces (area model

using a circle) One piece of gum from a package of gum that has

ten pieces (set model) A segment marked 0 to 1 on a number line where

the segment is divided into ten equal sections (linear number line)


Have students write word problems based on Fraction Representation Cards.

For example, if a student chose the “set model” card, he would write a fraction problem that could be solved using the representation on the card. Once corrected, another student could answer the problem

Students are using paper strips to make fraction kits. Ms. Alvarez notices Tyler labeling pieces as 1/7, which was not a directed step. He explained “When I counted them, there were seven, so I knew they were sevenths.”

Scenario: Modeling with fractionsGrades Taught: Third, fourth, and fifth

Consider…

Is Tyler necessarily correct?

Why / Why not?

What action, if any, do you take?

The Math…

Tyler lost one strip (1/8). Determining the size of a strip in relation

to the whole entails considering the number of copies of the strip needed to cover the whole.

Key Idea

The label on a fraction strip is not a fixed name, but a description of the relationship between the strip and the whole.


Pattern Block Fractions

Fraction Strips

Scenario: Comparison of fractionsTaught: Third and fourth grade

Consider:

Is he correct? After checking that Bruce

understands what the “>” symbol means, what action, if any, do you take?

The Math…

No he is not correct.

The correct equation is 1/6 < 1/4 because

one sixth is less than one quarter.

Key Idea:

The more pieces a whole is divided into, the smaller each piece will be.


Fraction Strips


Stacked Number Lines


Benchmark Fractions (0, ½, 1)

2/7______3/5

8/9______1/3

6/7______7/6

A group of students are investigating the books they have in their homes.

Steve notices that 1/2 of the books in his house are fiction books, while Andrew finds that 1/5 of the books his family owns are fiction.

Steve states that his family has more fiction books than Andrew’s.

Scenario: Comparison of FractionsTaught: Grades 3 and 4

Consider…

Is Steve necessarily correct?

Why / Why not?


The Math…

Steve is not necessarily correct because the amount of books that each fraction represents is dependent on the number of books each family owns.

For example…

Key Idea

The size of the fractional amount depends on the

size of the whole.

Classroom Activities to Support this Idea Provide opportunities for students to develop their

understanding of the importance of context in fraction comparison tasks.

Use materials and diagrams to demonstrate with clear examples, as in the previous tables.

Question the student about the size of one whole: Is one half always more than one fifth? What is the number of books we are finding one fifth

of? How many books is that? What is the number of books we are finding one half

of? How many books is that?

Luke labels the shaded portion of this fraction as ¼.

Scenario: Labeling fractionsGrades Taught: Third and fourth

Luke labels the shaded portion of this fraction as 1/3.

Cont.

He explains, “It’s just like the other one, only this time it’s one out of three, instead of one out of four.”

Consider…

Is Luke necessarily correct?

Why / Why not?


The Math…

Luke is not correct. Representing a fractional part of an area using fraction notation involves determining the whole area and then considering the size of the shaded part of the area in relation to the size of the whole.

Key Idea

Students understand that the size of a fractional part is relative to the size of the whole.


Provide opportunities for students to work with irregularly partitioned, and unpartitioned areas, lengths, and number lines.

Solution: Measurement Strategy

Consider the number of copies of the shaded part are needed to cover the whole. This is the denominator.

One of the copies is shaded (the numerator).

Solution: Part-Whole Strategy Divide the whole into parts of equal size. The whole is divided into equal parts by

inserting the dotted line.

Which shape has 1/3 of its area shaded?

Sarah insists that none of the shapes have 1/3 of their area shaded.

Scenario: Equivalent fractionsTaught: Third and fourth grades

Consider:

Do any of the shapes have 1/3 of their area shaded?


The Math…

Key Idea:

Equivalent fractions have the same value.


Fraction Strips


Stacked Number Lines

You observe the following equation in Emma’s work:

1/2 + 2/3 = 3/5

Is Emma correct?

Scenario: Addition of FractionsTaught: Grades 4 and 5

Consider…

You question Emma about her understanding and she explains:

“I ate 1 of the 2 sandwiches in my lunchbox, Kate ate 2 of the 3 sandwiches in her lunchbox, so together we ate 3 of the 5 sandwiches we had.”

What, if any, is the key understanding Emma needs to develop in order to solve this problem?

The Math…

Emma needs to know that the 1/2 relates to a different whole than the 2/3 .

If it is clarified that both lunchboxes together represent one whole, then the correct recording is: 1/5 + 2/5 = 3/5

Emma also needs to know that she has written an incorrect equation to show the addition of fractions.

Key Idea

When working with fractions, the whole needs to be clearly identified.


Question the student about their understanding. The one out of two sandwiches refers to

whose lunchbox? Whose lunchbox does the two out of three

sandwiches represent? Whose lunchbox does the three out of five

sandwiches represent? Use materials or diagrams to represent the

situation. For example:

Key Idea

When adding fractions, the units need to be the same because the answer can only have one denominator.


Use visuals to illustrate how to find a common denominator.


Estimate the sum with benchmark fractions; check for reasonableness. 0, ½,

and 1 can serve as reference points for estimation.

½ + 2/3= 1 1/6½ + ½ = 1

Anna says 7/3 is not possible as a fraction.

Scenario: Mixed NumbersTaught: Fourth and Fifth Grade

Consider…..

Is 7/3 possible as a fraction?


The Math…

Key Idea

A fraction can represent more than one whole. The denominator tells the number of equal parts into which a whole is divided. The numerator specifies the number of these parts being counted.


Use fraction strips or a number line to model

1/3 1/3 1/3

1/1/3 1/3 1/3

1/3

=1

=1/3

=1

1+1+ 1/3 =2 1/3

Katie solves the following problem: 2/3 x 5/7= 14/15

Scenario: Multiplication of FractionsTaught: Fourth and fifth grades

Consider…

Is Katie correct? What is the possible reasoning behind his

answer? What, if any, is the key understanding he

needs to develop in order to solve this problem?

The Math…

Katie is not correct. She has written the cross product as the numerator of the product and the other cross product as the denominator.

Key Idea

Students must grasp the concept behind multiplying fractions, beyond the algorithm.


Use grid pencils and colored pencils to demonstrate visually.Remember that “x” means “of.”

2/3 x 5/7 = 10/21

You observe the following equation in Bill’s work:2 ½ ÷ ½ = 1 ¼

Scenario: Division of FractionsTaught: Fifth grade

Consider…..

Is Bill correct? What is the possible reasoning

behind his answer? What, if any, is the key

understanding he needs to develop in order to solve this problem?

The Math…

No he is not correct. The correct equation is 2 ½ ÷ ½ = 5

Possible reasoning behind his answer: 1/2 of 2 1/2 is 1 1/4.

He is dividing by 2. He is multiplying by 1/2. He reasons that “division makes smaller” therefore

the answer must be smaller than 2 1/2.

Key Idea

To divide the number A by the number B is to find out how many lots of B are in A.

For example:

8÷2=4: There are 4 lots of 2 in 8

2 ½÷5=1/2: There are 5 lots of 1/2 in 2 1/2

• Varied visual representation (area, linear, set)• Fraction strips• Number lines• Benchmark fractions

Successful Strategies

Let’s Work on Our Own Fraction Sense!

Fractured Numbers-Problem of the Month

3-2-1 Reflection

3 ideas or pieces of knowledge you have found useful.

2 things you want to try with students. 1 question you’re still asking.

Sources

Institute of Education Sciences. Developing Effective Fractions Instruction for Kindergarten Through Eighth Grade. What Works Clearinghouse. 2010.McNamara, Julie. Beyond Pizzas & Pies. Math Solutions. Sausalito, 2010. Spangler, David. Strategies for Teaching Fractions: Using Error Analysis for Intervention and Assessment. Corwin. Thousand Oaks, 2011.

strategies to support student learning of fractions cynthia santosuosso

Documents