Transcript Decimals: Reading, Writing, and Rounding

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