1. Operations with Decimals
Addition, Subtraction, Multiplication, and Division
− × ÷

2. Rules for Adding Decimals
Write number sentence vertically.
Line up the decimals.
Add extra zeroes to keep place value.
Follow whole number addition rules.
Bring the decimal straight down in the sum.

3. Adding Decimals Example 1:
3.275
+5.600
8.875

4. Adding Decimals Example 2:
9.00
+2.04
11.04

5. Rules for Subtracting Decimals
Write number sentence vertically.
Line up the decimals.
Add extra zeroes to keep place value.
Follow whole number subtraction rules.
Bring the decimal straight down in the difference.

6. Subtracting Decimals Example 1:
17.3 – 2.48
17.30
-2.48
14.82 12 2 10 6

7. Subtracting Decimals Example 2:
78 – 3.09
78.00
- 3.09
74.91 9 7 10 10

8. Rules for Multiplying Decimals
Write number sentence vertically.
The number that has the most digits needs to be on top.
Do not line up the decimals.
Do not add zeroes.
Multiply following whole number multiplication rules.
Count how many digits are to the right of each decimal and add them together.
Move the decimal over to the left that many spaces.

9. Multiplying Decimals Example 1:
7.43
x 8.2
1486
+5944x
60.926 3 2
2 decimal places
1 decimal place 1 1
3 decimal places

10. Multiplying Decimals Example 2:
3.855
x 9.1
3855
+34695x 7 4 4
3 decimal places
1 decimal place 1 1 1
4 decimal places

11. Rules for Dividing Decimals
Write number sentence with the dividend in the “house” and the divisor on the “outside.”
Move the decimal in the divisor over until it is written as a whole number.
Move the decimal the same number of places over in the dividend.
Add zeroes if needed.
Move the decimal straight up.
Divide following whole number division rules.

12. Dividing Decimals Example 1:
57.2 ÷ 0.04
5720
2 decimal places in 0.04 1 4 3
Move 2 decimal places to the right in the divisor and dividend. -4 1 7
- 1 6 1 2
- 1 2
0 0
- 0

13. Dividing Decimals - Example 2:
1, ÷ 13.3 ,
,109.81
1 decimal places in 13.3
Move 1 decimal place to the right in the divisor and dividend.

14. LET’S PRACTICE - Multiply
3.7 × 1.23 =
2) 0.51 × 18 =
3) 4.3 × 2.1 =

15. LET’S PRACTICE - Divide
3.57 ÷ 3.5 =
2) 2.73 ÷ 0.65 =
3) ÷ 7.6 =