"Decimal Skills: Study Guide"

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Decimal Skills: Study Guide
What are decimals?
 Decimals are numbers we write using place value. They name parts of a whole when the
whole is divided into 10 equal parts (tenths), 100 equal parts (hundredths), 1000 equal
parts (thousandths), etc.
 A decimal is placed between the whole numbers and numbers that are parts of a whole.
Place Value Chart
Hundreds
Tens
Ones
Tenths
Hundredths
.
0
9
Read this number as nine tenths.
Hundreds
Tens
Ones
Tenths
Hundredths
.
0
5
6
Read this number as fifty-six hundredths.
Hundreds
Tens
Ones
Tenths
Hundredths
.
2
3
6
9
Read this number as two hundred thirty-six and nine tenths.
Hundreds
Tens
Ones
Tenths
Hundredths
.
1
1
5
6
Read this number as eleven and fifty-six hundredths.
Common Fractions and Their Decimal Amounts
(Remember: Think Money!)
1 =
1 =
3
=
0.25
0.75
0.5 or 0.50
2
4
4
Other Fractions and Decimals
6
=
6
=
35
=
0.6
0.06
0.35
10
100
100
Decimal Skills: Study Guide
What are decimals?
 Decimals are numbers we write using place value. They name parts of a whole when the
whole is divided into 10 equal parts (tenths), 100 equal parts (hundredths), 1000 equal
parts (thousandths), etc.
 A decimal is placed between the whole numbers and numbers that are parts of a whole.
Place Value Chart
Hundreds
Tens
Ones
Tenths
Hundredths
.
0
9
Read this number as nine tenths.
Hundreds
Tens
Ones
Tenths
Hundredths
.
0
5
6
Read this number as fifty-six hundredths.
Hundreds
Tens
Ones
Tenths
Hundredths
.
2
3
6
9
Read this number as two hundred thirty-six and nine tenths.
Hundreds
Tens
Ones
Tenths
Hundredths
.
1
1
5
6
Read this number as eleven and fifty-six hundredths.
Common Fractions and Their Decimal Amounts
(Remember: Think Money!)
1 =
1 =
3
=
0.25
0.75
0.5 or 0.50
2
4
4
Other Fractions and Decimals
6
=
6
=
35
=
0.6
0.06
0.35
10
100
100
Pictures That Represent Decimal Amounts
We commonly use squares to represent amounts when studying decimals, but anything divided
equally into 10, 100, 1000, etc., equal parts could be used.
We name decimals as tenths when the whole is divided into 10 equal parts.
The square is one whole. It is divided into 10 equal parts.
3 out of 10 are shaded
4 out of 10 are shaded
8 out of 10 are shaded
three tenths are shaded
four tenths are shaded
eight tenths are shaded
0.3
0.4
0.8
 These decimal amounts are in order from least to greatest.
We name decimals as hundredths when the whole is divided into 100 equal parts.
The square is one whole. It is divided into 100 equal parts.
37 out of 100 are shaded
65 out of 100 are shaded
82 out of 100 are shaded
thirty-seven hundredths are
sixty-five hundredths are shaded
eighty-two hundredths are shaded
shaded
0.82
0.65
0.37
 These decimal amounts are in order from least to greatest.
Whole numbers are written to the left of the decimal. Parts of the whole are written to the
right of the decimal. Here are some examples:
The shaded amount = two and seven tenths
The shaded amount = 2.7
1 whole
1 whole
7 out of 10 parts
The shaded amount = one and forty-three hundredths
The shaded amount = 1.43
1 whole
43 out of 100 parts
Comparing Decimal Amounts
 When comparing decimals, look at the largest places first. Compare using the
largest place that is different.
Compare using tenths place:
The digit in the tenths place is the same.
0.7 is greater than 0.4
Compare using hundredths:
0.7 > 0.4
0.43 is less than 0.48
0.43 < 0.48
Compare using tenths place:
Compare using tenths place: 0.7
0.7 is greater than 0.43
0.7 is the same as 0.70
0.7 > 0.43
0.7 = 0.70
(Remember that 0.7 = 0.70)
Adding and Subtracting Decimals
 When adding or subtracting decimals, you must add tenths to tenths and
hundredths to hundredths.
 This is easy to do if you line up the decimals carefully.
 Sometimes you may need to add a zero in the hundredths place to make
adding and subtracting easier.
Example:
4.9 – 1.25 =
4.90
- 1.25
3.6 5
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