1. Check your understanding What is 2.45 − 0.37? What is 4 – 3.78? What is 1.33 + 0.4?

2. Subtracting Across Zeroes If you have several zeroes in a row, and you need to borrow, go to the first digit that is not zero, and borrow. All middle zeroes become 9’s. The final zero becomes 10.

3. Example: 15 – 9.372 15 9.372 -.000 4 9 9 10 826.6 01 5 Subtracting Decimals

4. Use the grid below What addition problem is modeled by the following grid? A. 1.5 + 0.15 = 1.65 B. 1.45 + 0.2 = 1.65 C. 1.25 + 0.4 = 1.65 D. 1.2 + 0.45 = 1.65

5. What subtraction problem is modeled by the following grid? A. 1.57 − 0.33 = 1.24 B. 1.9 − 0.33 = 1.57 C. 1.9 − 0.37 = 1.53 D. 2 − 0.1 = 1.9

6. Write sentences for the sum of 0.06 and 0.04 using numbers and then using words. Numbers: _______ + _______ = _______ Words: _____ hundredths + ______ hundredths = _______ hundredths ________ hundredths + ________ hundredths = ______ tenth(s) How many hundredths are in one tenth?

7. Multiplying Decimals

8. Step 1: Multiply as if the factors were whole numbers

9. Step 1: 8.5 X2.5 4 2 5 1 7 0 0 2 1 2 5 next…..

10. Step 2: Count the total decimals places in the factors

11. Step 1: 8.5 X2.5 4 2 5 1 7 0 0 2 1 2 5 next…..

12. Step 3: Give the product the total decimal places of the factors

13. Step 1: 8.5 X2.5 4 2 5 1 7 0 0 2 1.2 5

14. Try These: 1. 4.8 2. 3.55 x 0.5 x.05

15. Answers: 1. 4.8 2. 3.55 x 0.5 x.05 = 2.40 = 0.1775

16. Review Multiplying decimals 1.0.403 x 5 = 2.524 x.05 = 3..15 x 0.31 =. 0465 2.015

17. Check your understanding You are multiplying 9.876 x 5.4321. How many decimal places does the answer have? A student says 19.8 x 3.1=612.8. Is this anwer correct? Explain how you know

18. Word Problem using decimals A year in Mars is 1.88 times as long as a year on Earth. An Earth year last 365.3 days. Find the length of year on Mars. 686.764 days

19. Word Problems David and Dora are close friends studying in the same school. David’s home is 6.87 miles away from school. Dora’s home is 7 times as far as David’s home from school. Find the distance between Dora’s school and her home. 48.09 miles