Take Out the Unit!

1. Lesson 10: I can subtract decimals using place value strategies and relate those strategies to a written method. 5th Grade Module 1 – Lesson 10

2. Take Out the Unit! Say the number... 76.358 Get your white boards ready… 76.358 = 7 tens _____ thousandths 6358 58 = 763 tenths ____ thousandths 7635 = ____ hundredths 8 thousandths 5th Grade Module 1 – Lesson 10

3. Add Decimals! Write the addition sentence in decimal form and solve. 0.3 + 0.2 = 0.5 3 tenths + 2 tenths = _______________ 0.05 + 0.04 = 0.09 5 hundredths + 4 hundredths = _______________ 0.35 + 0.04 = 0.39 35 hundredths + 4 hundredths = _______________ 5th Grade Module 1 – Lesson 10

4. One Unit Less Say the decimal that is one less than the given unit. 0.4 5 tenths 5 hundredths 5 thousandths 7 hundredths 9 tenths 0.04 0.004 0.06 0.8 5th Grade Module 1 – Lesson 10

5. One Unit Less Let’s switch it up a bit! 0.51 One tenth less than…. 0.61 One thousandth less than… 0.061 One hundredth less than… 0.549 0.060 0.539 5th Grade Module 1 – Lesson 10

6. Application Problem At the 2012 London Olympics, Michael Phelps won the gold medal in the men’s 100 meter butterfly. He swam the first 50 meters in 26.96 seconds. The second 50 meters took him 25.39. What was his total time? 5th Grade Module 1 – Lesson 10

7. Concept Development Have your place value chart, white board, and marker ready! Problem #1 5 tenths – 3 tenths = _______ Turn and tell your partner how you’ll solve this problem. Find the difference using your place value chart. 5th Grade Module 1 – Lesson 10

8. 7 ones 5 thousandths – 2 ones 3 thousandths Now, let’s cross off 2 ones and 3 thousandths to show the difference. Record your thinking vertically, using the algorithm. 5th Grade Module 1 – Lesson 10

9. Find the difference using your place value chart and record your thinking vertically. 9 hundreds 5 hundredths – 3 hundredths = _______ Read carefully, then tell your neighbor how you’ll solve this one. 5th Grade Module 1 – Lesson 10

10. Problem #2 83 tenths – 6.4 = _______ How is this problem different from the problems we’ve seen previously? Solve using your place value chart and record vertically using the standard algorithm. Share how you solved with your partner. 5th Grade Module 1 – Lesson 10

11. Standard Algorithm: • 8.3 • 6.4 1 9 5th Grade Module 1 – Lesson 10

12. Problem #3 9.2 – 6 ones 4 tenths = _______ Solve using disks and record vertically using the standard algorithm. Let’s share some different strategies of how you solved. 5th Grade Module 1 – Lesson 10

13. 0.831– 0.292 = _______ Solve using your place value chart and record vertically using the standard algorithm. Share how you solved. 5th Grade Module 1 – Lesson 10

14. 4.003 – 1.29 = _______ Solve using your place value chart and record vertically using the standard algorithm. What do notice about the thousandths place? Turn and talk to your partner. There is no digit in the thousandths place in 1.29. We can think of 29 hundredths as 290 thousandths. But in this case, I don’t have to change units because there are no thousandths that must be subtracted. 5th Grade Module 1 – Lesson 10

15. 6 – 0.48 = _______ Solve using your place value chart or with mental math and record vertically using the standard algorithm. What did we have to do to solve this problem? We had to think about 6 wholes in the same units as 48 hundredths. Therefore, we needed to record 6 ones as 600 hundredths or 6.00 in order to subtract vertically. Remember that we did not change the value by decomposing 6 wholes into 600 hundredths. 5th Grade Module 1 – Lesson 10

16. Problem Set Do your personal best to complete the Problem Set within 10 minutes. 5th Grade Module 1 – Lesson 10

17. Debrief How is subtracting decimal fractions the same as subtracting whole numbers? How is it different? In Problem 3(f), how did you think about finding the difference between 59 hundredths from 2 ones 4 tenths? Explain your approach. 5th Grade Module 1 – Lesson 10

18. Exit Ticket Time! 5th Grade Module 1 – Lesson 10