Notes: Decimal Basics

Writing Decimals Standard Form: 21.51

Word Form: twenty-one and fifty-one hundredths

Expanded Form: 20 + 1 + 0.5 + 0.01

Order from least to greatest: 9.02, 9.2, 9.002

1. Compare each place value. Line up decimals if needed.

2. Compare digits in the greatest place.

Comparing and Ordering Decimals Notes

1. 12.2 ___ 12.9

2. 5.4 ___ 5.40

3. 5.05 ___ 5.50

4. 0.098___ 0.98

5. 23.12___ 23.21

Examples

Round 76.285 to the nearest hundredth.

1. Underline the place value that you are rounding.

2. Circle the number to the right of it.

3. If the number to the right is 5 or greater, round up. If the number is less than 5, the place stays the same.

4. Drop off the numbers to the right of the place value that you are rounding to.

Rounding Decimals Notes

-

1.Put these numbers in order from least to greatest: 7.22, 70.2, 70.22, 7.02

2.Round these numbers to the nearest hundred:• 551• 6,423• 11,292.14

3.Write 416.203 in • expanded form:• word form:

Round each number to the nearest hundredth.

• 4.981

• 2.008

Round each number to the nearest tenth.

• 0.159

• 12.602

1.Write 123.9 in • expanded form:• word form:

2.Round 13.961 to the nearest tenth.

3.Round 5.6229 to the nearest hundredth.

4.Estimate $5.21 x $7.98 =

1.Write each decimal in standard form: • four tenths• five and seven hundredths

2.Fill in the blank with >, <, or =23.04 ___ 23.40 14.4 ___ 14.40

3. Round 123.991 to the nearest tenth.

4. Round 33.9123 to the nearest hundredth.

Adding and Subtracting Decimals*Remember to line up the decimals.

Ex: 5.4 – 1.23

Ex: 32.55 + 1.999

Decimal Computations

1.Multiply the factors like they are whole numbers.

2.Count how many numbers are to the right of the decimal in the original problem.

3.Begin at the right in the product, count over that many spaces, and put your decimal point.

Multiplying Decimals

Find the product.

• 1.6 x 2.8 3.15 x 2.3

• 3.1 x 77 42 x 4.8

Practice Problems

• 6.25 x 3 3. 3.36 x 2

• 4 x 1.9 4. 5.25 x 4.1

Dividing Decimals Vocab (pg. 13)

divisor

dividend

quotient

1.Move the decimal in the divisor all the way to the right.

2.Move the decimal point in the dividend the same number of places.

3.Divide as normal.

4.Place the decimal point in the answer in the same point above the place in the dividend.

Dividing Decimals Notes

Find the quotient.

6.37 ÷ 9.1 1.26 ÷ 0.9

11.24 ÷ 9 6 ÷ 0.12

Rounding Decimals for EstimationEstimate $3.79 + $2.12.

1. In your head, round to the easiest place.

2. Once numbers are rounded in your head, follow directions.

• You should be able to estimate all in your head! If you can’t you’ve made it too hard! Round to the easiest place for you!

Estimate each answer.

• $5.33 + 2.91 =

• 71 9 =

• 29 x 3.1 =

• 31 – 6 =