PLACE VALUE
WITH DECIMALS
How do I know what kind of
decimal it is?
 The name of a decimal is determined by the number
of places to the right of the decimal point
Number of Places Decimal Name Example
1 tenths 0.7
2 hundredths 0.05
3 thousandths 0.016
What are mixed decimals?
 Mixed decimals are numbers with both whole
numbers and decimals
 The name of a whole number is determined by the
number of places to the left of the decimal point
 In the number 128.765, 1 is in the hundreds place, 2 is in the
tens place, 8 is in the ones place, 7 is in the tenths place, 6 is
in the hundredths place, and 5 is in the thousandths place
How do you read decimals?
 To read a decimal correctly, first find the decimal
point
 Whole numbers are to the left of the decimal point;
any numbers to the right of a decimal point form a
decimal fraction
 Say “and” for the decimal point
 The decimal 2164.511 is read as “two thousand, one hundred
sixty-four and five hundred eleven thousandths”
Zeros after the decimal point
 Writing extra zeros after the decimal point
does not change the value!
 The decimals 0.2, 0.20, and 0.200 are
equivalent decimals
HERE ARE SOME PRACTICE
PROBLEMS IN WHICH I WILL
WORK THROUGH WITH YOU TO
MAKE SURE THAT YOU
UNDERSTAND THE MAIN
CONCEPTS COVERED.
Practice
Exercise 1
Write the decimals.
1. Five thousandths
2. Ninety-four thousandths
3. Three hundred thirty-six and sixty-nine
hundredths
Exercise 2
Write each decimal in words.
1. 7884.011
2. 5592.4
3. 4.203
4. 612.250
5. 10.44
Exercise 3
In what place (on the place value chart) is the
underlined digit? Write the answer.
1. 1.475
2. 3.763
3. 7780.215
4. 412.407
5. 902.103
Exercise 4
Write a decimal that has the same
number.
1. 0.2
2. 5.51
3. 410.6
4. 753.809
Adding and Subtracting Decimals
Essential Question:
 How do to add and subtract decimals?
Always line up decimals
Add and subtract like you always do
Bring decimal straight down in your
answers
Adding
Examples:
4.55 + 11.3
Put the first number on the
top of the second number
and line up the decimals.
4.55
+ 11.3
You can
add a zero
to help keep
everything
lined up
0
15.85
When adding or
subtracting you
always start
from the right
and work left.
6.44 + 16
When there is
not a decimal
put one
behind the
number.
Line up
the
decimal
6.44
+ 16.
Add a zero
to line up
everything
22.44
0
Subtracting
Examples:
5.34 -2.08
Put the first number on the
top of the second number
and line up the decimals.
5.34
-2.08
3.26
Different signs
Take difference
28 – 15.911
When there is
not a decimal
put one
behind the
number.
28.
-15.911
Add zeros to
line up
everything,
then subtract
000
7 9 9
8
0
.
2
1 9

Decimals

  • 1.
  • 2.
    How do Iknow what kind of decimal it is?  The name of a decimal is determined by the number of places to the right of the decimal point Number of Places Decimal Name Example 1 tenths 0.7 2 hundredths 0.05 3 thousandths 0.016
  • 3.
    What are mixeddecimals?  Mixed decimals are numbers with both whole numbers and decimals  The name of a whole number is determined by the number of places to the left of the decimal point  In the number 128.765, 1 is in the hundreds place, 2 is in the tens place, 8 is in the ones place, 7 is in the tenths place, 6 is in the hundredths place, and 5 is in the thousandths place
  • 4.
    How do youread decimals?  To read a decimal correctly, first find the decimal point  Whole numbers are to the left of the decimal point; any numbers to the right of a decimal point form a decimal fraction  Say “and” for the decimal point  The decimal 2164.511 is read as “two thousand, one hundred sixty-four and five hundred eleven thousandths”
  • 5.
    Zeros after thedecimal point  Writing extra zeros after the decimal point does not change the value!  The decimals 0.2, 0.20, and 0.200 are equivalent decimals
  • 6.
    HERE ARE SOMEPRACTICE PROBLEMS IN WHICH I WILL WORK THROUGH WITH YOU TO MAKE SURE THAT YOU UNDERSTAND THE MAIN CONCEPTS COVERED. Practice
  • 7.
    Exercise 1 Write thedecimals. 1. Five thousandths 2. Ninety-four thousandths 3. Three hundred thirty-six and sixty-nine hundredths
  • 8.
    Exercise 2 Write eachdecimal in words. 1. 7884.011 2. 5592.4 3. 4.203 4. 612.250 5. 10.44
  • 9.
    Exercise 3 In whatplace (on the place value chart) is the underlined digit? Write the answer. 1. 1.475 2. 3.763 3. 7780.215 4. 412.407 5. 902.103
  • 10.
    Exercise 4 Write adecimal that has the same number. 1. 0.2 2. 5.51 3. 410.6 4. 753.809
  • 11.
  • 12.
    Essential Question:  Howdo to add and subtract decimals? Always line up decimals Add and subtract like you always do Bring decimal straight down in your answers
  • 13.
    Adding Examples: 4.55 + 11.3 Putthe first number on the top of the second number and line up the decimals. 4.55 + 11.3 You can add a zero to help keep everything lined up 0 15.85 When adding or subtracting you always start from the right and work left.
  • 14.
    6.44 + 16 Whenthere is not a decimal put one behind the number. Line up the decimal 6.44 + 16. Add a zero to line up everything 22.44 0
  • 15.
    Subtracting Examples: 5.34 -2.08 Put thefirst number on the top of the second number and line up the decimals. 5.34 -2.08 3.26 Different signs Take difference
  • 16.
    28 – 15.911 Whenthere is not a decimal put one behind the number. 28. -15.911 Add zeros to line up everything, then subtract 000 7 9 9 8 0 . 2 1 9