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2.4: Decimal Addition

Difficulty Level: At Grade Created by: CK-12


Let's Think About It

Yoshi and his family have decided to have a yard sale. Yoshi's mother has him collect all the money from the customers. Yoshi wants to make sure that he is collecting the right amount from each person.The first person buys one item for $12.25, a second item for $0.50 and a third item for $0.75. Yoshi knows that he needs to add the decimals but isn't sure how to begin. How much money does the first person owe Yoshi?

In this concept, you will learn how to add decimals

Guidance

To add decimals, work with the wholes and parts of the numbers separately. Add the parts then add the wholes.

The best way to do this is to keep the parts together and keep the wholes together.

To do this, simply line up the decimal points in each number that you are adding.

Let's look at an example.

Add 3.45 + 2.37 = _____

In this problem you have parts and wholes. Let’s rewrite the problem vertically, lining up the decimal points.

3.45+ 2.37

Next, add the columns vertically and bring the decimal point down into the answer of the problem.

3.45+ 2.375.82

The answer is 5.82.

Let's look at another example.

5 + 3.45 + 0.56 = _______

In a problem like this, line up the decimal points, but add zeros to help hold places where there aren’t numbers. This helps keep the addition straight.

First, line up the problem vertically.

 

5.003.45+ 0.56

Notice that zeros help hold places where you did not have numbers. Now each number in the problem has the same number of digits.

Add the numbers.

5.003.45+ 0.569.01
 

The answer is 9.01.

Guided Practice

Add the following numbers.

13.25 + 0.80 + 1.30  = _____

First, line up the numbers vertically.

13.250.80+ 1.30

Then, add the numbers.

15.35

The answer is 15.35.

Examples

Add the following decimals.

Example 1

4.56 + 0.89 + 2.31 = _____

First, line up the numbers vertically.

 

4.560.89+ 2.31

Then, add the numbers.

7.76

The answer is 7.76.

Example 2

5.67 + 0.65 + 0.93 =_____

First, line up the numbers vertically.

  

5.670.65+ 0.93

Then, add the numbers.

7.25

The answer is 7.25.

Example 3

88.92 + 0.57 + 3.12 = _____

First, line up the numbers vertically.

88.920.57+3.12

Then, add the numbers.

92.61

The answer is 92.61.

Follow Up

Remember Yoshi and the yard sale? Yoshi's first customer wants to buy 3 different things.  To ask for the correct total amount, Yoshi needs to add $12.25, $0.50 and $0.75.  Can you find the total amount due?

First, line up the numbers vertically.

12.250.50+ 0.75

Then, add the numbers.

13.50

The answer is $13.50. Yoshi must collect $13.50 from the customer.

Video Review

Explore More

Add the following decimals.

1. 4.5 + 6.7 = _____

2. 3.45 + 2.1 = _____

3. 6.78 + 2.11 = _____

4. 5.56 + 3.02 = _____

5. 7.08 + 11.9 = _____

6. 1.24 + 6.5 = _____

7. 3.45 + .56 = _____

8. 87.6 + 98.76 = _____

9. 76.43 + 12.34 = _____

10. 5 + 17.21 = _____

11. 78 + 13.456 = _____

12. .456 + .23 + .97 = _____

13. 1.234 + 4.5 + 6.007 = _____

14. 3.045 + 3.3 + 9 = _____

15. 23 + 4.56 + .0091 = _____

Answers for Explore More Problems

To view the Explore More answers, open this PDF file and look for section 3.17. 

Image Attributions

Description

Difficulty Level:

At Grade

Grades:

Date Created:

Dec 02, 2015

Last Modified:

Dec 02, 2015
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