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Math 5Dividing Decimals
Instructor: Mrs. Tew Turner
In this lesson we will learn about dividing decimals.
Math Warm-upFind the perimeter
44 ft.
26 ft.
Math Warm-up ANSWERFind the perimeter
44 ft.
26 ft.
2 x (44 + 26) = 140 ft.
In this lesson we will answer the question:
How can you divide decimals?
Vocabulary Review
estimation - to give an approximate value rather than an exact answer.
Vocabulary Review
dividend- the number to be divided. 24 ÷ 4 = 6
divisor- the number that a dividend is divided by.24 ÷ 4 = 6
Vocabulary Review
quotient - the number that is the result of dividing. 24 ÷ 4 = 6
6 is the QUOTIENT!
Connecting to Previous Learning
Division is repeated subtraction. It is also used to divide an amount into equal sized groups, or a “fair share.” We use division because it is faster than subtracting a number over and over again, especially when dividing large numbers.
Remember the models we used to represent decimals in unit one?
ones tenths hundredths thousandths
This is how you draw these models in your math notebook.
ones tenths hundredthsthousandths
You will use the models to help you divide with decimals.
How would you solve this problem using models?
1.4 ÷2
Try it in your Math Notebook.
1.4 ÷2
Use the models to represent the dividend.
1.4 ÷2Next, divide the dividend into equal groups. For this problem it will be two equal groups because the divisor is 2.
How do you divide one whole into two parts?
1.4 ÷2Next, divide the dividend into equal groups. For this problem it will be two equal groups because the divisor is 2. You can think of
half of one whole as a fraction ½, which is 0.5 or 5 tenths=5/10.
1.4 ÷2Next, divide the dividend into equal groups. For this problem it will be two equal groups because the divisor is 2. Now, add the two
partial quotients: 0.2 + 0.5 = 0.7
One way would be to turn the dividend into tenths.
1.4 ÷2
1.4 = 10 tenths + 4 tenths = 14 tenths
Now, you can divide 14 tenths into 2 equal groups.
One way would be to turn the dividend into tenths.
1.4 ÷2
1.4 = 10 tenths + 4 tenths = 14 tenths
Each group contains 7 tenths. The answer is 0.7.
3.6 ÷ 1.2
Each section in this model represents the divisor, 1.2. The total amount represents the dividend, 3.6
3.6 ÷ 1.2 How many
groups of 1whole (called a flat) and 2 tenths (called rods) can be made out of 3 flats and 6 rods?
3.6 ÷ 1.2
The answer is 3.
4.83 ÷ 2.1
This will give you the quotient: 2.3.
Document Camera
Get your notebook
and pencil ready.
Make sure you
have the Lesson #
and date on your
page.
Guided Practice
2.4 ÷ 4
0.16 ÷ 4
84.6 ÷ 2
In your Math NotebookIndependent Practice
A relay race lasts 4.65 miles. The relay team has 3 runners. If each runner goes the same distance, how far does each team member run? Make an estimate, find your actual answer, and then compare them.
Independent Practice- ANSWER
My estimate is that each runner runs between 1 and 2 miles. If each runner went 2 miles, that would be a total of 6 miles which is too high. If each runner ran 1 mile, that would be 3 miles, which is too low.
Independent Practice- ANSWER
I used the 5 grids above to represent the 4.65 miles. I am going to use all of the first 4 grids and 65 of the squares in the 5th grid. I have to divide the 4 whole grids and the 65 squares into 3 equal groups.
Independent Practice- ANSWER
I labeled each of the first 3 grids for each runner, so I know that each team member ran at least 1 mile. I then have 1 whole grid and 65 squares to divide up. Each column represents one-tenth. If I give 5 columns to each runner, that means that each runner has run 1 whole mile and 5 tenths of a mile.
Independent Practice- ANSWER
Now, I have 15 squares left to divide up. Each runner gets 5 of those squares. So each runner ran 1 mile, 5 tenths and 5 hundredths of a mile. I can write that as 1.55 miles..
Independent Practice- ANSWER
When dividing with decimals, use models to help you group the dividend into equal groups.
Lesson Review
Quick Check1. Joe has 1.6 meters of rope. He
has to cut pieces of rope that are 0.2 meters long. How many can he cut?
2. Sean used 5 identical stones to form a path that was 9.7 meters long. How long was each of the stones?
In your Math Notebook
Quick CheckANSWERS
1. 1.6 ÷ 0.2 = 8
2. 9.7 ÷ 5 = 1.94
Today you learned how to divide with decimals.
Good Work with this
lesson.
