Reteach Lesson: Decimal Operations

Decimal Operations Lesson

​Adding, Subtracting, Multiplying, Dividing

​Adding Decimals

​To add decimals start by writing the amounts out and lining them up by their decimal points.

​

​​Remember to add in zero's as place holders if needed

Multiple Choice

86.04 + 4.04

• 9.044
• 9044
• 90.08
• 90.44

Multiple Choice

7.8 + 1.34 = 

• 9.14
• 2.12
• 6.46
• 8.42

​Subtracting Decimals

​Subtracting decimals is similar to adding decimals.

​

When subtracting decimals you are going to write out the two pieces to the problem by lining up the decimal points.

​

​Remember to add in zero's as place holders if needed

Multiple Choice

What is 3.8 - 3.19?

• 0.61

• 1.45

• 0.79

• 2.45

​Things to remember

• ​Line up the numbers by their decimal points to make sure they are in the corrct place value when adding or subtracting

• ​When adding be sure you are regrouping when needed

• ​When subtracting be sure you are borrowing when needed

Multiple Choice

What is 1.20 + 2.80?

• 3.1

• 4

• 2

• 4.2

Multiple Choice

What is 12.04 - 3.13?

• 9.01

• 8.91

• 4.32

• 11.64

​Multiplying Decimals

​1. When you multiply decimals you not line up the problem by the decimal points

​2. Starting from the right side of each number, count how many decimal places you have with each number.

​3. Add these together and write out to the side and circle it.

​4. Multiply as you usually would, starting from the right and working to the left.

​5. Put your place holder under the place value that you just multiplied and begin with your next number in the next place value if needed.

​6. Add these lines together.

​7. Move your decimal the correct amount of spaces in your product.

Multiple Choice

0.15 x 0.60

• 0.09
• 45
• 0.456
• 0.123

​Dividing Decimals by whole numbers

​1. Start by identifying the dividend and the divisor in your problem

​2. Rewrite the division problem using the division house with the dividend under the "house"

​3. Bring the decimal point straight up into the quotient

​4. Divide normally (think of how mnay times the divisor will go into the dividend)

​5. If you get a remainder other than 0, add a 0 to the dividend and bring down.

​6. Continue until you get a remainder of 0.

Multiple Choice

36.8 ÷ 2

• 18.4
• 16.4
• 18.04
• 1.84

​Dividing Decimals by Decimals

​​1. Start by identifying the dividend and the divisor in your problem

​2. Rewrite the division problem

using the division house with the

dividend under the "house"

​3. Move the decimal in your divisor

to the end of the number.

​4. Move your decimal in your

dividend the same number of spaces.

​5. Follow steps for dividing decimals by whole numbers

Multiple Choice

19.32 ÷ 2.3

• 8.4
• 7.2
• 8.9
• 8.6

​Review

Multiple Choice

Calculate
0.6÷5

• 0.1
• 0.12
• 0.012
• 1.02

Multiple Choice

If you multiply 0.73 by 2.52, how many times would you move the decimal?

• 2
• 3
• 4
• 5

Multiple Choice

4 x 0.03

• 12
• 0.12
• 120
• 0.012

Multiple Choice

7.05-4.6=

• 2.45
• 3.65
• 11.65
• 11.45

Multiple Choice

2.98+5.3=

• 2.51
• 8.28
• 3.63
• 2.37