1. Operations with Decimals!
Adding and Subtracting Decimals
How is adding and subtracting decimals similar to adding and subtracting whole numbers?

2. Activities 1-3 – See handout
Is there a relationship between adding and subtracting decimals and adding and subtracting whole numbers?
When in the real world would you add and subtract decimals?

3. Steps for adding and subtracting
Write the numbers down vertically.
Line up the decimal points.
Bring the decimal point straight down.
Add and subtract as you would whole numbers.

4. Examples
Add 8.13 and 2.76.
8.13
+2.76
Add
___

5. Examples
Subtract –
5.508
Subtract 21.9 –

6. Real – Life Application
$ $10.00
+$ ______

7. Your turn
Complete with your clock partner and then get your answers checked by me. =
27.9 – =

8. Conclusion
How is adding and subtracting decimals similar to adding and subtracting whole numbers?

9. Multiplying Decimals
How is multiplying decimals similar to and different from multiplying whole numbers?

10. Activity – Multiplying Decimals by Decimals
Complete Activity (pages 7 and 8)
What conjecture can you make about the relationships between multiplying decimals and multiplying whole numbers?

12. Steps to Multiplying Decimals
Multiply as you would with whole numbers.
Count the number of decimal places in the decimal factor.
The product has the same number of decimal places.

13. Examples
It is helpful to estimate to see if your answer is reasonable!
Find 6 x 3.91
Find 3 x

14. Examples
Multiply 4.8 x 7.2.
Multiply 3.1 x 0.05.

15. Real Life Application
You buy 2.5 pounds of tomatoes. You hand the cashier a $10 bill. How much change should you receive?

16. Conclusion
How is multiplying decimals similar to and different from multiplying whole numbers?

17. How can you model decimal division with pattern blocks and numbers?
Dividing Decimals
How can you model decimal division with pattern blocks and numbers?

18. Complete Activity 1 on Division Modeling
Dividing decimals by whole numbers
Place the decimal point in the quotient above the decimal point in the dividend.
Then divide as you would with whole numbers.
Find 7.6 ÷ 4 Find 36.4 ÷ 2

19. Dividing Decimals by Decimals
Multiply the divisor and dividend by a power of ten to make the divisor a whole number.
Place the decimal point in the quotient and divide as you would with whole numbers.

20. Examples
Find 18.2 ÷ 1.4.
Find 9.6 ÷ 1.2
Find ÷ 0.51

21. Real – World Example

22. Summary
How can you model decimal division with pattern blocks and numbers?
How else can you divide if you don’t draw or use a model?