NOYCE, 7/07/11•Fractions: Equivalence and Representation

WARM-UP: WHAT APPROACHES TO FRACTIONS HAVE YOU SEEN AND/OR USED?

Conceptual approaches What is the unit? Part to whole relationships Ratios and proportions Decimals, percents, and connections to fractions Comparison of fractions Connections with division

Representation Pattern blocks Fraction circles Fraction rectangles Fraction bars Number line

REPRESENTATION OF FRACTIONS AS POINTS IN THE COORDINATE PLANE

On graph paper, create a coordinate plane with the origin in the middle of the page.

Plot the following points, so that the Numerator is the y-coordinate, and Denominator is the x-coordinate

What do you notice?

1

2,2

4,3

6,

5

10, 2

4, 4

8

MORE FRACTIONS REPRESENTED ON THIS LINE?

Find another 2 fractions that are represented on this line. Plot their points.

Find another 2 points on this line, which do not have positive coordinates. What fractions do they represent?

Find another 2 points on this line which do not have integer coordinates. What fractions do they represent?

WHAT ABOUT THE ORIGIN??

Did you choose the origin as one of your points? Why or why not?

Does the origin also represent a fraction as the other points do? Why or why not?

SOME MORE LINES

Now plot (on the same coordinate plane) the representations of the following fractions:

Connect the points in each set with a line. Let’s call the lines L1, L2, and L3.

What relationships do you see between the lines? What is similar and what is different?

2

3,

8

12, 4

6,

1

1.5,

3

4.5

1

3,

1

3,

4

12, 3

9, 5

15

WE NOW HAVE…

CONNECTIONS: FRACTIONS AND SLOPE OF LINES THROUGH THE ORIGIN

What can we say about the relationships between the fractions represented by points on one line?

What can we say about the relationships between fractions and slope?

What can we say about the relationships between fractions represented on different lines?

CONNECTIONS: FRACTIONS AND SLOPE OF LINES THROUGH THE ORIGIN

What can we say about the relationships between the fractions represented by points on one line? All fractions represented by points on one line through

the origin are equivalent. What can we say about the relationships between

fractions and slope? Any fraction represented by a point on a line is the

slope of the line. All the slopes thus noted are equivalent, since all

fractions represented on the same line are equivalent. What can we say about the relationships between

fractions represented on different lines? These fractions are not equivalent.

SIMPLFIYING FRACTIONS TO LOWEST TERMS

Use the fraction-line connection to simplify the following fractions

6

18

14

16

4

10

SIMPLIFYING FRACTIONS TO LOWEST TERMS

Use the fraction-line connection to simplify the following fractions

6

18

1

3

14

16

7

8

4

10

2

5

COMPARING FRACTIONS

Take a new sheet of graph paper, and create a coordinate plane.

Use the ideas we’ve just discussed to compare the values of the following pairs of fractions:

a)

b)

c)

2

5 and

3

8

5

2 and

8

3

5

2 and

8

3

CONNECTION TO RIGHT TRIANGLES AND THE TANGENT FUNCTION

y

8 10

x 4 1 5

CONNECTION TO RIGHT TRIANGLES AND THE TANGENT FUNCTION

-1 -4 x

-10 -8

y

-5

CONNECTION TO RIGHT TRIANGLES AND THE TANGENT FUNCTION

Bruce drew triangle ABC using the following coordinates: (0,0), (5,0), and(5,-4). Give the coordinates of the vertices for two other triangles similar to triangle ABCthat are in different quadrants created by rotation about the origin.

What are the coordinates of the vertices for each triangle?

What is the scale factor of each triangle? What are the angle measurements for each

triangle?

TANGENT TABLE

DEBRIEF

In what ways does this approach to the relationship between fractions and lines enhance your students’ understanding of one or the other or both?

What standards at your grade level can be addressed either by this approach?

Where might you include this kind of activity in your teaching?

RESOURCES

Lombard, B. and Fulton, B. Simply Great Math Activities; Fractions Decimals, and Percents.

Schuster, L. and Anderson, N. Good Questions for Math Teaching.

Additional material using graph paper can be found at

https://docs.google.com/viewer?url=http://www.tttpress.com/pdf/CAMT-2004-Fraction-Finder-Handout.pdf