A. Introduction to the Unit
In the second grade, students learned about unit fractions (1/3, 1/4, 2/5, etc.) and proper fractions by examining equally divided geometric figures. They also learned to compare, add, and subtract common fractions having the same denominator. In the first semester of third grade, they extended their understanding of the fraction representing the quantity.
In this unit, students learn the mutual relationships between common fractions and decimals by equating a one-place (tenths) decimal with a common fraction whose denominator is 10; by comparing decimals; by adding decimals with sums up to 1; and by subtracting decimals with minuends up to 1.
Students express length, volume, and weight using decimals. They also use number lines to increase their understanding of the concept of decimals as a different expression of fractions.
The contents of this unit are followed in fourth grade by units covering hundredth and thousandth (two- and three-place) decimals, as well as addition and subtraction of decimals.
The textbook for this unit is structured as follows:
Main content
- Understanding decimals
- Students master the concept of 0.1 as a different expression of 1/10 by examining the relationship between liters and deciliters (metric units of volume).
- Comparing decimals
- Students use common fractions with the denominator 10 to understand the comparison of decimals. They also compare decimals by figuring out how many 0.1's are represented by the numeral in the tenths place. They increase their understanding of the relationship between common fractions and decimals by comparing decimal tenths with common fractions whose denominator is 10.
- Adding decimals
- The addition of decimals is introduced through real-life situations. Students come to understand the principle of addition using the number line. Also, they increase their efficiency of computation by formalizing the method for adding decimals.
- Subtracting decimals
- The subtraction of decimals numbers is introduced through real-life situations. Students come to understand the principle of subtraction using the number line. Also, they increase their efficiency of computation by formalizing the method for subtracting decimals.
Practice
- Supplementary and intensive studies
- Students apply the mastered content to solve problems involving expression, comparison, addition, and subtraction of decimals, and to solve word problems using addition and subtraction of decimals.
B. Unit Objectives
Students will be able to:
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