UNIT X 74 | UNIT 2 Instructional Routine: Mathematics p. Txxxii Use Decimal Place Value A • Listen to media to build academic language Play the audio once for students to gain a general understanding of the information without looking at the text. Then replay it, this time asking students to read along silently. Direct them to pay special attention to the words in bold and their context. • Review fractions Write some examples of fractions on the board. ( 1/ 2, 1/ 10, 1/ 3) Elicit from students that a fraction shows how many parts of a whole there are. The top number (the numerator) expresses the number of parts. The bottom number (the denominator) says how many equal parts the whole is divided into. Review each example on the board. • Review decimals Write some examples of decimals on the board. (1.25, 0.5, 3.75, 0.75) Elicit from students that a decimal number can be defined as a number where the whole number part and the fractional part is separated by a decimal point. The dot in a decimal number is called a decimal point. The whole number part comes before (to the left of) the decimal point and the fraction part comes after (to the right of) the decimal point. For each example on the board, ask: Does it have a whole number part? What is the fractional part? Read and discuss the Place Value box. • Define word and standard form Students should note that decimals are linked to fractions and that there are many ways of showing a number. Elicit from students the difference between word form, standard form, and expanded form. It is easiest to place a value above each number first and then change the different forms. • Understand place value Explain that a number line is one way to compare decimals. Draw a number line and ask students to write the decimal fractions in order. Discuss how to use greater than and less than symbols to compare numbers. Essential Question: How can you use place value to understand the size and meaning of numbers? Read the Essential Question aloud and ask students to share their ideas about place value. Write responses on the board. Confirm or correct students’ ideas after completing the activities. ANSWERS Sample answer: The value of digits depends on their placement before and after the decimal point. To the left of the decimal point, the greater the number of places, the higher the value of the number. To the right of the decimal point, the greater the number of places, the more precisely is the part of the whole is expressed. EXPLORE AND LEARN DIFFERENTIATED INSTRUCTION Scaffold Measurements can be challenging for students to work with if they do not have concrete examples. Work with students to create number lines and cut out squares of paper labelled to represent the different place values. Students can mix these up and order them until they are familiar with the values to the right and left of a decimal point. Amplify Students can write five decimal numbers for their partner to plot on a number line. Then pairs can test each other on which decimal number is greater than or less than another. Use Decimal Place Value Place Value The place of a digit in a number determines its value. Place value helps you to determine the size of a number. A decimal shows a part of a whole number. A decimal point goes between the whole number and the decimal part. tens ones tenths hundredths thousandths 5 6 8 9 7 word form fifty-six and eight hundred ninety-seven thousandths standard form 56.897 expanded form 5 x 10 + 6 x 1 + 8 x 1 10 + 9 x 1 100 + 7 x 1 1,000 You can use a number line to compare decimals. A number line shows numbers in order from least to greatest. The decimals with the smaller values are on the left. The value of the decimals increases as you move to the right. You can use greater than (>) and less than (<) symbols to compare numbers. 53.83 < 54.50 54.93 > 54.65 A Read about decimal place value. • How can you use place value to understand the size and meaning of numbers? ? ESSENTIAL QUESTION 53 53.5 54.5 54 55 UNIT 2 74 CONNECT TO Mathematics UNIT 2 / CONNECT TO MATHEMATICS
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