Basic Math

Divide decimals | Fifth Grade

Divide Decimals - Fifth Grade Math

Complete Notes & Formulas

1. Estimate Decimal Quotients

What is Estimation?

Estimation means finding an approximate answer by rounding decimals before dividing.

Two Methods for Estimation

Method 1: Rounding

Step 1: Round the dividend (number being divided) to the nearest whole number

Step 2: Round the divisor (number dividing by) to the nearest whole number

Step 3: Divide the rounded numbers

Method 2: Compatible Numbers

Compatible numbers are numbers that are easy to divide mentally. They divide evenly with no remainder.

Step 1: Find compatible numbers close to the actual numbers

Step 2: Use basic division facts

Step 3: Calculate the quotient

Formula

Estimated Quotient = (Rounded Dividend) ÷ (Rounded Divisor)

Examples

Example 1 (Rounding): Estimate 62.9 ÷ 7.48

• 62.9 rounds to 63

• 7.48 rounds to 7

• 63 ÷ 7 = 9

Estimated Quotient ≈ 9

Example 2 (Compatible Numbers): Estimate 23.8 ÷ 4.75

• 23.8 is close to 24

• 4.75 is close to 4

• 24 and 4 are compatible (24 ÷ 4 = 6)

Estimated Quotient ≈ 6

When to Use Estimation

✓ To check if your answer is reasonable

✓ When an approximate answer is acceptable

✗ Do NOT use when exact answers are required

2. Divide Decimals Using Blocks: Complete the Equation

Base Ten Blocks Representation

Flat = 1 whole = 1.0

Rod (Long) = 1 tenth = 0.1

Cube (Unit) = 1 hundredth = 0.01

Steps to Divide Using Blocks

Step 1: Represent the dividend (number being divided) using base ten blocks

Step 2: Divide the blocks into equal groups based on the divisor

Step 3: If needed, trade larger blocks for smaller ones (1 flat = 10 rods, 1 rod = 10 cubes)

Step 4: Distribute all blocks equally into groups

Step 5: Count the value in ONE group to find the quotient

Key Concept

The quotient equals the amount in each equal group

Examples

Example 1: 1.4 ÷ 7 = ?

• Represent 1.4 → 1 flat + 4 rods

• Trade 1 flat for 10 rods → Total: 14 rods (14 tenths)

• Divide 14 rods into 7 equal groups

• Each group has 2 rods = 0.2

Answer: 1.4 ÷ 7 = 0.2

Example 2: 0.63 ÷ 3 = ?

• Represent 0.63 → 6 rods + 3 cubes

• Divide 6 rods into 3 groups → 2 rods per group

• Divide 3 cubes into 3 groups → 1 cube per group

• Each group has 2 rods + 1 cube = 0.2 + 0.01 = 0.21

Answer: 0.63 ÷ 3 = 0.21

3. Divide Decimals Using Area Models: Complete the Equation

What is an Area Model?

An area model represents division as a rectangle where the area is the dividend, one side is the divisor, and the other side is the quotient.

Area = Length × Width

Dividend = Divisor × Quotient

Steps to Use Area Model

Step 1: Treat decimals as whole numbers temporarily

Step 2: Break the dividend into parts that are easier to divide

Step 3: Divide each part by the divisor

Step 4: Add the partial quotients together

Step 5: Place the decimal point in the correct position

Example

Divide: 225.5 ÷ 5

Step 1: Remove decimal: 2255 ÷ 5

Step 2: Break 2255 into parts: 2000 + 200 + 50 + 5

Step 3: Divide each part:

2000 ÷ 5 = 400

200 ÷ 5 = 40

50 ÷ 5 = 10

5 ÷ 5 = 1

Step 4: Add: 400 + 40 + 10 + 1 = 451

Step 5: Place decimal: 225.5 ÷ 5 = 45.1

Answer: 45.1

4. Divide Decimals by Whole Numbers Using Place Value

The Place Value Method

This method uses understanding of place value to divide decimals mentally or with simple calculations.

Key Rules

• Think about the dividend in terms of its place value units (ones, tenths, hundredths)

• Convert to the same unit (all tenths, all hundredths, etc.)

• Divide as whole numbers, then adjust the place value

Steps

Step 1: Identify the place value of the decimal

Step 2: Think of the decimal as a whole number (in tenths, hundredths, etc.)

Step 3: Divide the whole numbers

Step 4: Adjust the answer to match the place value

Examples

Example 1: 8.4 ÷ 2

• 8.4 = 84 tenths

• 84 tenths ÷ 2 = 42 tenths

• 42 tenths = 4.2

Answer: 4.2

Example 2: 0.48 ÷ 4

• 0.48 = 48 hundredths

• 48 hundredths ÷ 4 = 12 hundredths

• 12 hundredths = 0.12

Answer: 0.12

5. Divide Decimals by Whole Numbers Without Adding Zeros

What Does This Mean?

These are division problems where the decimal divides evenly without a remainder, so no extra zeros are needed.

Long Division Steps

Step 1: Set up the division problem (dividend inside, divisor outside)

Step 2: Place the decimal point in the quotient directly above the decimal in the dividend

Step 3: Divide as if working with whole numbers

Step 4: Bring down digits one at a time

Step 5: Continue until remainder is 0

Key Rule

Keep the decimal point in the quotient directly above the decimal point in the dividend

Examples

Example 1: 8.4 ÷ 4

• 4 ) 8.4

• 8 ÷ 4 = 2 (place above the 8)

• Place decimal point above dividend's decimal

• Bring down 4: 4 ÷ 4 = 1

• Answer: 2.1

Example 2: 6.75 ÷ 5

• 6 ÷ 5 = 1 remainder 1

• Bring down 7: 17 ÷ 5 = 3 remainder 2

• Place decimal point

• Bring down 5: 25 ÷ 5 = 5

• Answer: 1.35

6. Division with Decimal Quotients

What is a Decimal Quotient?

A decimal quotient is an answer that includes a decimal point, even when dividing two whole numbers.

When Do We Get Decimal Quotients?

• When the dividend doesn't divide evenly by the divisor

• When we continue dividing past the whole number part

• When we add zeros to the dividend to continue dividing

Steps

Step 1: Divide as usual with whole numbers

Step 2: If there's a remainder, add a decimal point to the quotient

Step 3: Add a zero to the dividend after the decimal point

Step 4: Bring down the zero and continue dividing

Step 5: Repeat until remainder is 0 or you have enough decimal places

Formula

Whole Number ÷ Whole Number = Decimal (when it doesn't divide evenly)

Examples

Example 1: 7 ÷ 4

• 7 ÷ 4 = 1 remainder 3

• Add decimal: 1.

• Add zero to dividend: 7.0 → bring down 0 → 30

• 30 ÷ 4 = 7 remainder 2

• Add another zero: 20 ÷ 4 = 5

• Answer: 1.75

Example 2: 9 ÷ 8

• 9 ÷ 8 = 1 remainder 1

• Add decimal and zero: 1._ → 10 ÷ 8 = 1 remainder 2

• Add another zero: 20 ÷ 8 = 2 remainder 4

• Add another zero: 40 ÷ 8 = 5

• Answer: 1.125

7. Division with Decimal Quotients and Rounding

Why Round?

Sometimes division produces a quotient with too many decimal places or a quotient that repeats forever. We round to make it more practical.

Rounding Rules

If the digit to the right is 5 or greater → Round UP (add 1 to the rounding place)

If the digit to the right is less than 5 → Round DOWN (keep the digit the same)

Common Rounding Places

Nearest tenth: 1 decimal place (0.1)

Nearest hundredth: 2 decimal places (0.01)

Nearest thousandth: 3 decimal places (0.001)

Steps

Step 1: Divide until you have one more decimal place than needed

Step 2: Look at the digit in the place right after your rounding place

Step 3: Apply the rounding rule

Step 4: Drop all digits after the rounding place

Examples

Example 1: 10 ÷ 3 (round to nearest hundredth)

• 10 ÷ 3 = 3.333333... (repeating)

• Divide to 3 decimal places: 3.333

• Look at third decimal place: 3

• 3 < 5, so round DOWN

• Answer: 3.33

Example 2: 22 ÷ 7 (round to nearest tenth)

• 22 ÷ 7 = 3.142857...

• Divide to 2 decimal places: 3.14

• Look at hundredths place: 4

• 4 < 5, so round DOWN

• Answer: 3.1

8. Division with Decimal Quotients: Word Problems

Key Words for Division

Shared equally

Divided into groups

Each person gets

Per, each, every

How many in each?

Average, mean

Steps to Solve Word Problems

Step 1: Read the problem carefully

Step 2: Identify what you're trying to find

Step 3: Find the dividend (total amount) and divisor (number of groups)

Step 4: Write the division equation

Step 5: Solve and check if the answer makes sense

Examples

Example 1: Sarah bought 5 pounds of apples for $8.75. What is the cost per pound?

Find: Cost per pound

Total cost: $8.75 (dividend)

Number of pounds: 5 (divisor)

Equation: $8.75 ÷ 5

Calculate: 8.75 ÷ 5 = 1.75

Answer: $1.75 per pound

Example 2: A ribbon is 12.6 meters long. It is cut into 9 equal pieces. How long is each piece?

Find: Length of each piece

Total length: 12.6 meters (dividend)

Number of pieces: 9 (divisor)

Equation: 12.6 ÷ 9

Calculate: 12.6 ÷ 9 = 1.4

Answer: 1.4 meters per piece

9. Divide by Decimals Using Place Value

The Key Concept

To divide by a decimal, convert the divisor to a whole number by multiplying BOTH the dividend and divisor by the same power of 10.

Why Does This Work?

Multiplying both numbers by the same amount doesn't change the quotient. It's like equivalent fractions!

6 ÷ 2 = 3

(6 × 10) ÷ (2 × 10) = 60 ÷ 20 = 3

Same answer!

Steps

Step 1: Count how many decimal places are in the divisor

Step 2: Move the decimal point in the divisor to the RIGHT to make it a whole number

Step 3: Move the decimal point in the dividend to the RIGHT the same number of places

Step 4: Divide as usual with the new numbers

Examples

Example 1: 4.5 ÷ 0.5

• Divisor 0.5 has 1 decimal place

• Move decimal 1 place RIGHT in both numbers:

→ 0.5 becomes 5

→ 4.5 becomes 45

• Now divide: 45 ÷ 5 = 9

• Answer: 9

Example 2: 0.63 ÷ 0.09

• Divisor 0.09 has 2 decimal places

• Move decimal 2 places RIGHT in both:

→ 0.09 becomes 9

→ 0.63 becomes 63

• Now divide: 63 ÷ 9 = 7

• Answer: 7

10. Divide by Decimals Without Adding Zeros

What This Means

These problems divide evenly after converting the divisor to a whole number, so no extra zeros are needed in the dividend.

Steps

Step 1: Move the decimal in the divisor to make it a whole number

Step 2: Move the decimal in the dividend the same number of places

Step 3: Place the decimal point in the quotient above the new position in the dividend

Step 4: Divide as usual

Step 5: The division completes with no remainder

Examples

Example 1: 3.6 ÷ 1.2

• Move decimal 1 place RIGHT:

→ 1.2 becomes 12

→ 3.6 becomes 36

• Divide: 36 ÷ 12 = 3

• Answer: 3

Example 2: 8.4 ÷ 0.7

• Move decimal 1 place RIGHT:

→ 0.7 becomes 7

→ 8.4 becomes 84

• Divide: 84 ÷ 7 = 12

• Answer: 12

11. Divide by Decimals (Complete Method)

The Universal Rule

Make the divisor a whole number, then divide!

Complete Steps

Step 1: Write the division problem

Step 2: Count decimal places in the divisor

Step 3: Move both decimal points RIGHT by that amount

Step 4: Add zeros to the dividend if needed

Step 5: Place the decimal point in the quotient

Step 6: Divide using long division

Step 7: Add zeros after the dividend's decimal point if there's a remainder

Step 8: Continue until remainder is 0 or round as instructed

Examples

Example 1: 5.75 ÷ 2.5

• Divisor has 1 decimal place

• Move decimals 1 place RIGHT:

→ 2.5 becomes 25

→ 5.75 becomes 57.5

• Divide: 57.5 ÷ 25

• 575 ÷ 25 = 23 (thinking in tenths)

• Place decimal: 2.3

• Answer: 2.3

Example 2: 7.65 ÷ 0.15

• Divisor has 2 decimal places

• Move decimals 2 places RIGHT:

→ 0.15 becomes 15

→ 7.65 becomes 765

• Divide: 765 ÷ 15 = 51

• Answer: 51

Quick Reference: Division Steps Summary

Division TypeKey StepExample
Decimal ÷ Whole NumberKeep decimal point aligned6.4 ÷ 2 = 3.2
Whole Number ÷ Whole NumberAdd zeros after decimal if needed7 ÷ 4 = 1.75
Decimal ÷ DecimalMake divisor a whole number first4.8 ÷ 0.6 = 8

💡 Important Tips to Remember

Always make the divisor a whole number when dividing by decimals

✓ Move decimal points the same number of places in both dividend and divisor

Line up the decimal point in your quotient with the decimal in the dividend

Add zeros to the dividend if needed to continue dividing

✓ Use estimation to check if your answer is reasonable

✓ When rounding, divide to one more place than required

✓ In word problems, identify key words that signal division

Check your work by multiplying: quotient × divisor should equal dividend

🧠 Memory Tricks for Decimal Division

Trick 1: "Move Move Divide"
When dividing by a decimal: Move the decimal in the divisor, move it the same way in the dividend, then divide!

Trick 2: "Straight Up"
The decimal point in your answer goes straight up from the decimal point in the dividend.

Trick 3: "Make It Whole"
Always turn the divisor into a whole number first—it makes division much easier!

Trick 4: "Check with Multiplication"
Answer × Divisor = Dividend (If it doesn't, check your work!)

Master Decimal Division! 🎯

Practice different types of problems daily to build confidence and speed!

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