1. Title of Notes: Adding and Subtracting Decimals
pg. 15 & 16

2. when we add or subtract money we vertically align the decimal point.
This way we are sure to add digits with the same place value.
We use this same procedure for any decimal numbers.

3. Add:
To add digits with the same place value, we align decimal points.
In this problem the whole number 3 has the same place value as the 6 and the 4.
We place a decimal point to the right of the 3 and align decimal points.
We may fill empty decimal places with zeros if we wish.

4. The rules do not change for adding and subtracting
1). Line up the decimal points.
2). Add or subtract each column just as you would add or subtract integers.
3). Remember the rules for adding and subtracting integers and fractions.
The rules do not change for adding and subtracting

5. Remember… Adding positive/negative numbers: Same signs, add and keep.
Different signs, subtract.
Subtracting positive/negative numbers:
Change to plus the opposite.
Follow addition rules.

6. Example 1: =
13.40
+ 7.28
20.68

7. 12.32 + 3.88 -16.20 Example 2: -3.88 + -12.32 = Keep the sign!
(Same signs, add and keep)

8. Example 3:
15.24 =
- 8.60
-6.64
Keep the sign of the
larger number!
(Different signs, subtract)

9. Example 4:
2.100 =
- .004
-2.096
Keep the sign of the
larger number!
(Different signs, subtract)

10. Example 5:
34.65 =
-19.25
Keep the sign of the
larger number!
(Different signs, subtract)

11. Find the perimeter of the triangle.
Example 6:
Find the perimeter of the triangle.
12.5
4.3 +
7.6
24.4