1. 6.2.4 Adding & Subtracting Decimals

2. Base Ten Blocks = 1 one = 1 tenth = 1 hundredth = 1.00 = .10 = .01
= 1 Dollar
= 1 Dime
= 1 Penny

3. Combining Blocks
= 1 one, 2 tenths, 3 hundredths = = 1.23
= 0 one, 8 tenths, 7 hundredths =
= 0.87

4. Adding Blocks
How many tenths are there? 10 How many hundredths are there? +
Can the hundredths or tenths be traded up?
YES!

5. Trading Up =
10 hundredths = = +
1 tenth + =
10 tenths =
1 one

6. Putting It All Together
1 one + 1 one = 2 ones + 1 ten = 2 ones and 1 ten = = 2.10

7. Adding & Subtracting Decimals
Step #1: Line up the decimals
Step #2: Add or subtract as usual (as if the decimal isn’t there)
– – –

8. Your Turn!
90.31 – 72.04
17 – 58.23
– 86.1

9. Homework
Page 82 (3, 4, 5, 9, 11, 16, 17, 18, 19, 20, 24, 26, 30, 31)