Add and subtract decimals (5.N.B.T.7) NYS Math Module 1 Lesson 10 Objective: Subtract decimals using place value strategies and relate those strategies to a written method. I can... Add and subtract decimals (5.N.B.T.7) Take out the unit (5.N.B.T.1)
Take out the Unit Say this number: 76.358 = 7 tens _____ thousandths 6358 76.358 = 763 tenths _____ thousandths 58 76.358 = _____ hundredths 8 thousandths 7635
Adding Decimals Write the following addition sentence in decimal form. 3 tenths + 2 tenths = _______ Now solve it: 0.3 + 0.2 = _____ 0.5 Two more. Rewrite them in decimal form and solve 5 hundredths + 4 hundredths = _______ 0.05 + 0.04 = 0.09 35 hundredths + 4 hundredths = _______ 0.35 + 0.04 = 0.39
One Unit Less Say the decimal that is one less than the unit given. 5 tenths 3 tenths 1 tenth Let’s try it with hundredths. 5 hundredths 3 hundredths 1 hundredth Let’s try it with thousandths. 5 thousandths 3 thousandths 1 thousandth
0.029 0.028 0.51 0.06 Write the decimal that is one less thousandth. What is one tenth less than 0.61? 0.51 0.06 What is 1 thousandth less than 0.061?
One more.. 0.539 What is one hundredth less than 0.549?
.Word 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 seconds. What was his total time? 52.35
Since they are both tenths, you can simply subtract 5 – 3. .Concept Development Read this problem aloud: 5 tenths – 3 tenths = _______ 2 tenths Tell your partner how you are going to solve this problem.: Since they are both tenths, you can simply subtract 5 – 3.
Only LIKE units are being subtracted Some tips to remember. Write the decimals in standard form. Line up the decimals. Add zeros in all the empty spaces. Find the difference: 7 ones 5 thousandths – 2 ones 3 thousandths Only LIKE units are being subtracted 7.005 2.003 - 5.002
- 900.05 000.03 900.02 Read carefully and rewrite the decimals. 9 hundreds 5 hundredths – 3 hundredths Tell your neighbor how to solve this one. Now, solve it vertically. 900.05 000.03 - 900.02
83 tenths – 6.4 = _____ How is this problem different from the problems we’ve done previously? Write it vertically or use your place value chart, so you can see the difference. 8.3 6.4 - 7 1 We need to regroup. 1.9
Try another one on your own. 9.2 – 6 ones 4 tenths = _____ Discuss how you solved this problem with a partner. 9.2 6.4 - 8 1 Did you regroup? 2.8
0.831 – 0.292 = _____ How did you solve this problem? First, write the problem vertically. Make sure you regroup. 7 12 0.831 0.292 - 1 0.539
4.003 – 1.29 = _____ Rewrite the problem vertically. What do you notice about the thousandths place? Turn and tell your partner. That’s right. We need to add a zero So instead of 29 hundredths, we think of it as 290 thousandths. Solve it. 39 1 4.003 1.290 - 2.713
- 59 6.00 0.48 1 6 – 0.48 = _____ 5.52 Say this problem aloud. How can we think of 6 wholes in the same units as 48 hundredths? Is there another way to write 6 wholes? 59 1 6.00 0.48 - 5.52
Let’s try one more: 13.2 – 5.08 1 1 13.20 05.08 - 08.12
Problem Set Review 5 1 5.1 4 3 40.3 Example #1: 5 ones 3 tenths – 2 tenths = ______ones______tenths=_____ 5 1 5.1 3 tenths – 2 tenths = 1 tenth There is only 5 ones, so 5 – 0 = 5 Rewrite 5 ones and 1 tenth You try: 4 tens 8 tenths – 5 tenths = ______tens______tenths=_____ 4 3 40.3
- - 2.6 – 0.4 = 2.6 0.4 2.2 6 – 15 tenths = 6.00 1.50 4.50 Example #2: 1.) Rewrite the problem 2.) Solve it 2.2 Example #3: 6 – 15 tenths = - 6.00 1.50 1.) Rewrite the problem 4.50 2.) Add “zeros” if needed 3.) Solve it
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Exit Ticket Exit Ticket Exit Ticket Exit Ticket Subtract 1.7 – 0.8 = ______ tenths - ______ tenths = _______ tenths=_______ Subtract vertically, showing all work. a. 84.637 – 28.56 = _________ b. 7 – 0.35 = __________ Subtract 1.7 – 0.8 = ______ tenths - ______ tenths = _______ tenths=_______ Subtract vertically, showing all work. a. 84.637 – 28.56 = _________ b. 7 – 0.35 = __________ Exit Ticket Exit Ticket Subtract 1.7 – 0.8 = ______ tenths - ______ tenths = _______ tenths=_______ Subtract vertically, showing all work. a. 84.637 – 28.56 = _________ b. 7 – 0.35 = __________ Subtract 1.7 – 0.8 = ______ tenths - ______ tenths = _______ tenths=_______ Subtract vertically, showing all work. a. 84.637 – 28.56 = _________ b. 7 – 0.35 = __________