Text Reflections

Ch. 14, 15, 16, 17

Chapter 14

Algebraic Thinking: Generalizations, Patterns, and Functions


1. Algebra is a useful tool for generalizing arithmetic and representing patterns and regularities in our world.


2. Symbolism, especially involving equality and variables, must be

well understood conceptually for students to be successful in

mathematics, particularly algebra.


3. Methods we use to compute and the structures in our number system can and should be generalized. For example, the generalization


Algebraic Thinking


There are three strands of algebraic reasoning, all three infusing the central notions of generalization and symbolization:


1. Study of structures in the number system, including

those arising in arithmetic (algebra as generalized

arithmetic)

2. Study of patterns, relations, and functions

3. Process of mathematical modeling


The Meaning of Variables


Expressions or equations with variables are a means for expressing patterns and generalizations. When students can work with expressions involving variables without even thinking about the specific number or numbers that the letters may stand for.

Chapter 15

Developing Fraction Concepts

1. For students to really understand fractions, they must experience fractions across many constructs, including part of a whole, ratios, and division.


2. Three categories of models exist for working with fractions, area (example: 1/3 of a garden), length (example 3/4 of an inch), and set or quantity (example: 1/2 of the class).


3. Partitioning and iterating are ways for students to understand the

meaning of fractions, especially numerators and denominators.


4. Students need many experiences estimating with fractions.


Meanings of Fractions


Fractions are a critical foundation for students, as they are used in measurement across various professions, and they are essential to the study of algebra and more advanced mathematics.


Fraction Constructs


Understanding fractions means understanding all the pos­sible concepts that fractions can represent. One of the com­monly used meanings of fraction is part‐whole, including

examples when part of a whole is shaded.


Part‐Whole: Using the part‐whole construct is an effec­tive starting point for building meaning of fractions. Part‐whole goes well beyond shading a region. For example, it could be part of a group of people (3/5 of the class went on the field trip), or it could be part of a length (we walked 3 1/2 miles).


Measurement: Measurement involves identifying a length and then using that length as a measurement piece to determine the length of an object. For example, in the fraction 5/8, you can use the unit fraction 1/8 as the selected length and then count or measure to show that it takes five of those to reach 5/8.


Division: Consider the idea of sharing $10 with 4 peo­ple. This is not a part‐whole scenario, but it still means that each person will receive one‐fourth (1/4) of the money, or 2 1/2 dollars. Division is often not connected to fractions, which is unfortunate.

Chapter 16

Developing Strategies for Fraction Computation


1. The meanings of each operation with fractions are the same as

the meanings for the operations with whole numbers. Operations with fractions should begin by applying these same meanings to fractional parts.


●For addition and subtraction, the numerator tells the number of parts and the denominator the unit. The parts are added or subtracted.

●Repeated addition and area models support development of

concepts and algorithms for multiplication of fractions.

●Partition and measurement models lead to two different

thought processes for division of fractions.


2. Estimation should be an integral part of computation development to keep students’ attention on the meanings


Conceptual Development Takes Time


It is important to give students ample opportunity to develop fraction number sense prior to and during instruc­tion about common denominators and other procedures for computation.


The Common Core State Standards suggests the following develop­mental process:


Grade 4: Adding and subtracting of fractions with like denominators, and multiplication of fractions by whole numbers.


Grade 5: Developing fluency with addition and sub­traction of fractions, and developing understanding of the multiplication of fractions and of division of fractions in limited cases (unit fractions divided by whole numbers and whole numbers divided by unit

fractions).


Grade 6: Completing understanding of division of fractions.


A Problem‐Based Number-Sense Approach


Students should understand and have access to a variety of ways to solve fraction computation problems. In many cases, a mental or invented strategy can be applied, and a standard algorithm is not needed. The goal is to prepare students who are flexible in how they approach fraction computation.


The following guidelines should be kept in mind when developing computational strategies for fractions:


1. Use contextual tasks.

2. Explore each operation with a variety of models.

3. Let estimation and informal methods play a big role in the

development of strategies.

4. Address common misconceptions regarding computational

procedures.


Computational Estimation


Estimation is one of the most effective ways to build under­standing and procedural fluency with fractions. There are different ways to estimate fraction sums and differences :


1. Benchmarks

2. Relative size of unit fractions.

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Chapter 17

Developing Concepts of Decimals and Percents




Decimals are critically important in many occupations. For nurses, pharmacists, and workers building airplanes, for example, the level of precision affects safety for the general public. Because students and teachers have been shown to have greater difficulty understanding decimals than fractions, conceptual understanding of decimals and their connections to fractions must be carefully developed.



Extending the Place-Value System



Before exploring decimal numerals with students, it is advisable to review ideas of whole-number place value. One of the most basic of these ideas is the 10-to-1 multiplicative relationship between the values of any two adjacent positions.



A Two-Way Relationship: The 10-makes-1 rule continues indefinitely to larger and larger pieces or positional values.



Regrouping: Even at this stage, students need to be reminded of the powerful concept of regrouping. Flexible thinking about place values should be practiced prior to

exploring decimals. Students should revisit not just making 1 ten from 10 units, but thinking about regrouping 2,451 into 24 hundreds, 245 tens or 2,451 ones.



The Role of the Decimal Point: Students must know that the decimal point marks the location of the ones (or units) place. On many calculators, when there is a whole number answer no decimal point appears—only when the ones place needs to be identified will the decimal point show in the display. Students also need to see that adding zeros to

the left of a whole number will have no consequence and adding zeros to the right of a decimal fraction will not change the number.

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