Decimals: Reading, Writing, and Rounding

Section 4.1

Objectives

• Write word names from place value names and place value names from word names • Round a given decimal

Objective 1: Write word names from place value names and place value names from word names

Objective 1

• Decimal numbers (commonly called decimals) – another way of writing fractions and mixed numbers • Decimal point – separates the whole number part from the fraction part • Number of decimal places – number of digits to the right of the decimal point

Objective 1

• Place values for decimals – Same as whole numbers for the digits to the left of the decimal point – Fraction whose denominator is 10, 100, 100, etc., for digits to the right of the decimal point • Hundreds, tens, ones, tenths, hundredths, thousandths, etc.

• If decimal point is not written, it is understood to follow the ones place • Expanded form

Objective 1

• • To write word name 1. Write name of whole number that is left of decimal point 2.

Write “and” for the decimal point 3. Write whole number name of number that is to right of decimal point 4. Write place value of digit farthest to right If number has only zero or no number left of decimal, omit step 1 and 2

Objective 1

• To write place value name 1. Write whole number (the number before “and”) 2.

Write decimal point for the word “and” 3. Ignore place value name, and write name for number following “and”. Insert zeros, if necessary, between decimal point and the digits following it to ensure the correct place value.

Objective 2: Round a given decimal

Objective 2

• Exact decimals – exact values • Approximate decimals – rounded values • Decimals are rounded using same procedures as whole numbers

Objective 2

• To round a decimal number – Draw an arrow under the given place value – If digit to right of arrow is 5, 6, 7, 8, 9, then round up – If digit to right of arrow is 1, 2, 3, 4, then digit at the arrow stays the same – Write zeros, if necessary, to right of arrow