Unit 7 3rd grade cs 2012 2013

Isaac School District, No. 5
Mathematics Curriculum Guide: Third Grade

Unit 7
Finding Fair Shares
Fractions and Decimals Total Sessions: 16
Big Ideas: Essential Questions:
Students will understand that:
 When might you use fractions?
 Fractions represent equal parts or equal-sized portions of a whole set.
 How are parts of a whole represented?

 How are parts of a set represented?

 What does it mean to be close to a whole?
Unit Vocabulary: fraction, denominator, numerator, equivalent fractions, decimal, decimal point

Domain: Operations and Algebraic Thinking (OA)

AZ Math Standards Mathematical Practices
Cluster: Represent and solve problems involving multiplication and division.

Students are expected to:
3.OA.3. Use multiplication and division within 100 to solve word problems in situations 3.MP.1. Make sense of problems and persevere in solving them.
involving equal groups, arrays, and measurement quantities, e.g., by using drawings
and equations with a symbol for the unknown number to represent the problem. (See 3.MP.4. Model with mathematics.
Table 2.)
3.MP.7. Look for and make use of structure.
Connections: 3.RI.7; ET03-S1C1-01
Explanations and Examples
Students use a variety of representations for creating and solving one-step word problems, i.e., numbers, words, pictures, physical objects, or equations. They use multiplication
and division of whole numbers up to 10 x10. Students explain their thinking, show their work by using at least one representation, and verify that their answer is reasonable.
Continued on next page

Third Grade Underline = Tier 2 words
Investigation Unit 7
Created on 2/4/2012 7:02 PM
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Word problems may be represented in multiple ways:
 Equations: 3 x 4 = ?, 4 x 3 = ?, 12 ÷ 4 = ? and 12 ÷ 3 = ?
 Array:

 Equal groups

 Repeated addition: 4 + 4 + 4 or repeated subtraction
 Three equal jumps forward from 0 on the number line to 12 or three equal jumps backwards from 12 to 0

Examples of division problems:
 Determining the number of objects in each share (partitive division, where the size of the groups is unknown):
o The bag has 92 hair clips, and Laura and her three friends want to share them equally. How many hair clips will each person receive?

 Determining the number of shares (measurement division, where the number of groups is unknown)
Third Grade the monkey loves bananas. Molly, his trainer, has 24 bananas. Underline = Tier 24words
Max If she gives Max bananas each day, how many days will the bananas last?
Created on 2/4/2012 7:02 PM 1
Starting Day Day 2 Day 3 Day 4 Day 5 Day 6
24 24-4= 20-4= 16-4= 12-4= 8-4= 4-4= - 2 -
20 16 12 8 4 0

Solution: The bananas will last for 6 days.
Students may use interactive whiteboards to show work and justify their thinking.


Cluster: Understand properties of multiplication and the relationship between multiplication and division.

3.OA.5. Apply properties of operations as strategies to multiply and divide. (Students 3.MP.1. Make sense of problems and persevere in solving them.
need not use formal terms for these properties.) Examples: If 6 × 4 = 24 is known,
then 4 × 6 = 24 is also known. (Commutative property of multiplication.) 3 × 5 × 2 can 3.MP.4. Model with mathematics.
be found by 3 × 5 = 15, then 15 × 2 = 30, or by 5 × 2 = 10, then 3 × 10 = 30.
(Associative property of multiplication.) Knowing that 8 × 5 = 40 and 8 × 2 = 16, one 3.MP.7. Look for and make use of structure.
can find 8 × 7 as 8 × (5 + 2) = (8 × 5) + (8 × 2) = 40 + 16 = 56. (Distributive property.)
*Extensions Necessary to involve fractions 3.MP.8. Look for and express regularity in repeated reasoning.
Connections: 3.OA.1; 3.OA.3; 3.RI 4; 3.RI.7; 3.W.2; ET03-S1C4-01
Students represent expressions using various objects, pictures, words and symbols in order to develop their understanding of properties. They multiply by 1 and 0 and divide by
1. They change the order of numbers to determine that the order of numbers does not make a difference in multiplication (but does make a difference in division). Given three
factors, they investigate changing the order of how they multiply the numbers to determine that changing the order does not change the product. They also decompose numbers
to build fluency with multiplication.
Models help build understanding of the commutative property:

Example: 3 x 6 = 6 x 3

In the following diagram it may not be obvious that 3 groups of 6 is the same as 6 groups of 3. A student may need to count to verify this.
Error! Filename not specified. is the same quantity as Error! Filename not specified.

Continued on next page

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Example: 4 x 3 = 3 x 4
An array explicitly demonstrates the concept of the commutative property.

4 rows of 3 or 4 x 3 3 rows of 4 or 3 x 4

Students are introduced to the distributive property of multiplication over addition as a strategy for using products they know to solve products they don’t know. For example, if
students are asked to find the product of 7 x 8, they might decompose 7 into 5 and 2 and then multiply 5 x 8 and 2 x 8 to arrive at 40 + 16 or 56. Students should learn that they
can decompose either of the factors. It is important to note that the students may record their thinking in different ways.

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5 x 8 = 40 7 x 4 = 28
2 x 8 = 16 7 x 4 = 28
To further develop understanding of properties related to multiplication and 56
56 division, students use different representations and their understanding of the relationship between
multiplication and division to determine if the following types of equations are true or false.
 0 x 7 = 7 x 0 = 0 (Zero Property of Multiplication)
 1 x 9 = 9 x 1 = 9 (Multiplicative Identity Property of 1)
 3 x 6 = 6 x 3 (Commutative Property)
 8 ÷ 2 = 2 ÷ 8 (Students are only to determine that these are not equal)
 2 x 3 x 5 = 6 x 5
 10 x 2 < 5 x 2 x 2
 2 x 3 x 5 = 10 x 3
 0 x 6 > 3 x 0 x 2

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Domain: Number and Operations – Fractions (NF)

Cluster: Develop understanding of fractions as numbers.
(Grade 3 expectations in this domain are limited to fractions with denominators 2, 3, 4, 6, and 8.)
3.NF.1. Understand a fraction 1/b as the quantity formed by 1 part when a whole is 3.MP.1. Make sense of problems and persevere in solving them.
partitioned into b equal parts; understand a fraction a/b as the quantity formed by a
parts of size 1/b. 3.MP.4. Model with mathematics

Connections: ET03-S1C2-02; ET03-S1C4-02 3.MP.7. Look for and make use of structure.


Some important concepts related to developing understanding of fractions include:
 Understand fractional parts must be equal-sized
Example Non-example

These are thirds These are NOT thirds

 The number of equal parts tell how many make a whole
 As the number of equal pieces in the whole increases, the size of the fractional pieces decreases
 The size of the fractional part is relative to the whole
o The number of children in one-half of a classroom is different than the number of children in one-half of a school. (the whole in each set is different
therefore the half in each set will be different)

Continued on next page.

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 When a whole is cut into equal parts, the denominator represents the number of equal parts
 The numerator of a fraction is the count of the number of equal parts
o ¾ means that there are 3 one-fourths
o Students can count one fourth, two fourths, three fourths

Students express fractions as fair sharing, parts of a whole, and parts of a set. They use various contexts (candy bars, fruit, and cakes) and a variety of models (circles, squares,
rectangles, fraction bars, and number lines) to develop understanding of fractions and represent fractions. Students need many opportunities to solve word problems that require
fair sharing.
To develop understanding of fair shares, students first participate in situations where the number of objects is greater than the number of children and then progress into
situations where the number of objects is less than the number of children.
Examples:
 Four children share six brownies so that each child receives a fair share. How many brownies will each child receive?
 Six children share four brownies so that each child receives a fair share. What portion of each brownie will each child receive?
 What fraction of the rectangle is shaded? How might you draw the rectangle in another way but with the same fraction shaded?

2 1
Solution: or
4 2

What fraction of the set is black?

2
Solution:
6

1
Solution:
3

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3.NF.2. Understand a fraction as a number on the number line; represent fractions on 3.MP.1. Make sense of problems and persevere in solving them.
a number line diagram.
a. Represent a fraction 1/b on a number line diagram by defining the interval from 0 3.MP.4. Model with mathematics
to 1 as the whole and partitioning it into b equal parts. Recognize that each part
has size 1/b and that the endpoint of the part based at 0 locates the number 1/b 3.MP.7. Look for and make use of structure...
on the number line.
b. Represent a fraction a/b on a number line diagram by marking off a lengths 1/b
from 0. Recognize that the resulting interval has size a/b and that its endpoint
locates the number a/b on the number line.

Connections: 3.RI.7; 3.SL.1; ET03-S1C4-01

Students transfer their understanding of parts of a whole to partition a number line into equal parts. There are two new concepts addressed in this standard which students
should have time to develop.
1. On a number line from 0 to 1, students can partition (divide) it into equal parts and recognize that each segmented part represents the same length.

2. Students label each fractional part based on how far it is from zero to the endpoint.

An interactive whiteboard may be used to help students develop these concepts.
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3.NF.3. Explain equivalence of fractions in special cases, and compare fractions by 3.MP.1. Make sense of problems and persevere in solving them.
reasoning about their size.
a. Understand two fractions as equivalent (equal) if they are the same 3.MP.2. Reason abstractly and quantitatively.
size, or the same point on a number line.
b. Recognize and generate simple equivalent fractions, e.g., 1/2 = 2/4, 4/6 3.MP.3. Construct viable arguments and critique the reasoning of others.
= 2/3). Explain why the fractions are equivalent, e.g., by using a visual
fraction model. 3.MP.4. Model with mathematics.
c. Express whole numbers as fractions, and recognize fractions that are
equivalent to whole numbers. Examples: Express 3 in the form 3 = 3/1; 3.MP.6. Attend to precision.
recognize that 6/1 = 6; locate 4/4 and 1 at the same point of a number
line diagram. 3.MP.7. Look for and make use of structure.
d. Compare two fractions with the same numerator or the same
denominator by reasoning about their size. Recognize that comparisons 3.MP.8. Look for and express regularity in repeated reasoning.
are valid only when the two fractions refer to the same whole. Record
the results of comparisons with the symbols >, =, or <, and justify the
conclusions, e.g., by using a visual fraction model.

Connections: 3.NF.1; 3NF.2; 3.RI.3; 3.SL.1; 3.SL.3; ET03-S1C4-01
1 1
An important concept when comparing fractions is to look at the size of the parts and the number of the parts. For example, 8 is smaller than 2 because when 1 whole is cut
into 8 pieces, the pieces are much smaller than when 1 whole is cut into 2 pieces.

Students recognize when examining fractions with common denominators, the wholes have been divided into the same number of equal parts. So the fraction with the larger
numerator has the larger number of equal parts.
2 5
6 6

To compare fractions that have the same numerator but different denominators, students understand that each fraction has the same number of equal parts but the size of the
parts are different. They can infer that the same number of smaller pieces is less than the same number of bigger pieces.
3 3
8 4

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Domain: Measurement and Data (MD)

Cluster: Solve problems involving measurement and estimation of intervals of time, liquid volumes, and masses
of objects.
3.MD.1. Tell and write time to the nearest minute and measure time intervals in 3.MP.1. Make sense of problems and persevere in solving them.
minutes. Solve word problems involving addition and subtraction of time intervals in
minutes, e.g., by representing the problem on a number line diagram. 3.MP.4. Model with mathematics.
(Sessions: What time is it routine)
*Extensions Necessary 3.MP.6. Attend to precision.
Connections: 3.RI.3; 3.RI.7; ET03-S1C4-01


Students in second grade learned to tell time to the nearest five minutes. In third grade, they extend telling time and measure elapsed time both in and out of context using clocks
and number lines.

Students may use an interactive whiteboard to demonstrate understanding and justify their thinking.

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Domain: Geometry (G)

Cluster: Reason with shapes and their attributes.
3.G.1. Understand that shapes in different categories (e.g., rhombuses, rectangles, 3.MP.5. Use appropriate tools strategically.
and others) may share attributes (e.g., having four sides), and that the shared
attributes can define a larger category (e.g., quadrilaterals). Recognize rhombuses, 3.MP.6. Attend to precision.
rectangles, and squares as examples of quadrilaterals, and draw examples of
quadrilaterals that do not belong to any of these subcategories. 3.MP.7. Look for and make use of structure.

Connections: 3.RI.3; 3.RI.4; ET03-S2C2-01

In second grade, students identify and draw triangles, quadrilaterals, pentagons, and hexagons. Third graders build on this experience and further investigate quadrilaterals
(technology may be used during this exploration). Students recognize shapes that are and are not quadrilaterals by examining the properties of the geometric figures. They
conceptualize that a quadrilateral must be a closed figure with four straight sides and begin to notice characteristics of the angles and the relationship between opposite sides.
Students should be encouraged to provide details and use proper vocabulary when describing the properties of quadrilaterals. They sort geometric figures (see examples below)
and identify squares, rectangles, and rhombuses as quadrilaterals.

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3.G.2. Partition shapes into parts with equal areas. Express the area of each part as a 3.MP.2. Reason abstractly and quantitatively.
unit fraction of the whole. For example, partition a shape into 4 parts with equal area,
and describe the area of each part as 1/4 of the area of the shape. 3.MP. 4. Model with mathematics.

Connections: 3.MD.7; 3.NF.1; 3.RI.7; 3.MP.5. Use appropriate tools strategically..
ET03-S1C1-01

Given a shape, students partition it into equal parts, recognizing that these parts all have the same area. They identify the fractional name of each part and are able to partition a
shape into parts with equal areas in several different ways.
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Unit 7 3rd grade cs 2012 2013

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Unit 7 3rd grade cs 2012 2013