The document discusses adding, subtracting, and multiplying decimals using decimal grids. It reviews place value and represents decimals as fractions on a 10x10 grid. Students are instructed how to use the grid to model decimal operations like 0.4 + 0.5 by shading in the appropriate number of squares. Examples are provided and students are asked to solve additional problems using the decimal grid method.

1. Adding, Subtracting, and
Multiplying Decimals
Topic 1.1

2. Review: Place Values
Thousands
Hundreds
Tens
Ones
Decimal
Tenths
Hundredths
Thousandths
Ten-Thousandths
0 0 0 0 . 0 0 0 0
3 4 2 2 . 1 2 3 4Example:

3. Review: Place Values as Fractions
Thousands
Hundreds
Tens
Ones
Decimal
Tenths
Hundredths
Thousandths
Ten-Thousandths
0 0 0 0 . 0 0 0 0
1 . 1/10

4. Decimal Grids + Fractions
This grid is a 10 x 10
grid which means it
has ____ squares
1 2 3 4 5 6 7 8 9 10
12345678910
If I shade in all of the squares I’ll have ______ shaded squares
If I shade in half of the squares I’ll have _______ shaded squares
One fully shaded square is equal to one whole

5. Decimal Grids + Fractions
1 2 3 4 5 6 7 8 9 10
12345678910
= 1
1 2 3 4 5 6 7 8 9 10
12345678910
= 0.5
Because all 100 squares are filled in Because half of the 100 squares are filled in

6. Decimal Grids + Fractions
1 2 3 4 5 6 7 8 9 10
12345678910
= 0.2
1 2 3 4 5 6 7 8 9 10
12345678910
= 0.7
Because 20 out of 100 squares are filled in Because 70 out of 100 squares are filled in

7. Decimal Grids + Fractions
1 2 3 4 5 6 7 8 9 10
12345678910
Now, lets model 0.8 on the grid
0.8 = 8/10
8/10 of 100 is 80
So, how many squares should I fill in?

8. Adding on Decimal Grids (To the tenths place)
1 2 3 4 5 6 7 8 9 10
12345678910
Let’s take it a step further…. Consider the following equation:
0.4 + 0.5 = ?
Let’s shade in 0.4 first…
Now, let’s add 0.5 (or 50 squares)
How many squares are filled in now?
What would that be as a decimal?

9. Adding on Decimal Grids (To the hundredths place)
1 2 3 4 5 6 7 8 9 10
12345678910
Let’s take it a step further…. Consider the following equation:
0.42 + 0.54 = ?
Let’s shade in 0.42 first…
Now, let’s add 0.54 (or 54 squares)
How many squares are filled in now?
What would that be as a decimal?

10. At your tables…
1.Solve: 0.5 + 0.4
2.Solve: 0.32 + 0.26
3.Solve: 0.8 + 0.4

11. Subtracting on Decimal Grids (To the tenths
place)1 2 3 4 5 6 7 8 9 10
12345678910
Let’s take it a step further…. Consider the following equation:
0.5 - 0.4 = ?
Let’s shade in 0.5 first…
Now, take away 0.4 (or 40 squares)
How many squares are filled in now?
What would that be as a decimal?

12. At your tables…
1.Solve: 0.6 - 0.5
2.Solve: 0.55 - 0.28
3.Solve: 1 - 0.4

13. Multiplying on Decimal Grids
(To the tenths place)
1 2 3 4 5 6 7 8 9 10
12345678910
Let’s try multiplying 0.4 x 0.3
Fill in 0.4 first (vertically)
Then fill in 0.3 (horizontally)
Now, find where they overlap
There are 12 squares covered which means our answer is…
0.12

14. At your tables…
1.Solve: 0.5 x 0.2
2.Solve: 0.3 x 0.1
3.Solve: 0.2 x 0.6