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# q1-day32-subdecimals by JuyeeDasNair

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```									                           Mathematics Alignment Lesson
Grade 5 Quarter 1 Day 32

Common Core State Standard(s)                                     Alignment Lesson
5.NBT.7 Add, subtract, multiply, and divide                          Subtracting Decimals
decimals to hundredths, using concrete
models or drawings and strategies based on      1. Discuss Journal Prompt question from yesterday’s homework.
place value, properties of operations, and/or          Explain how you would use base ten blocks to solve the
the relationship between addition and                  problem 1.85 – 0.97. Use appropriate math vocabulary in
subtraction; relate the strategy to a written          your explanation.
method and explain the reasoning used.          2. Display Transparency/Blackline Master, “Problem Solving
with Decimals” and present the Incorrect Change problem.
Standards for Mathematical Practice            3. Give students a couple of minutes to turn and talk to a partner
1. Make sense of problems and persevere in         about the Incorrect Change problem. Then engage students in
solving them.                                   Math Talk to make sense of the problem. Be sure to discuss
2. Reason abstractly and quantitatively.           how using mental estimation might have helped Aiden know
3. Construct viable arguments and critique         the cashier had given her incorrect change.
the reasoning of others.
4. Present the Distance Traveled problem to students and have
6. Attend to precision.
students work in pairs to find a solution, using any method
that makes sense to them.
Materials Needed:                    5. Use Math Talk to have pairs of students share a variety of
   Blackline Masters, “Subtracting                solution strategies, making sure to include someone who used
Decimals, Subtracting Decimals             a more standard algorithm. You may wish to incorporate
Journal Prompt”                         some of the following questions into your discussion as
   Transparencies/Blackline Masters,              appropriate:
“Problem Solving with Decimals,                 How can finding an estimate help determine if our
Find the Missing Decimal                       answer makes sense?
Number”                                 Why does it work to line up the places when we
   MathBoard materials                                    subtract decimals using a vertical algorithm?
   Base Ten Blocks available for each                  How does our discussion about “ungrouping” from
student as needed (flats, rods, units)                 yesterday connect to the algorithm?
 How does the algorithm connect to the base ten blocks
we used yesterday? …to the base ten grids we shaded?
6. Display Transparency/Blackline Master, “Find the Missing
Assessment                          Decimal Number.” Have students work in pairs to complete
Informal:                                          the activity. As students work, circulate to monitor their
 Assess student solution strategies and           understanding of the decimal subtraction algorithm.
discussion during partner work,             7. Use Math Talk to have students share solutions. Be sure to
independent work, and math talk.               connect solution strategies to the algorithm.
 Journal Prompt explanation                    8. Use the remaining time for students to practice and discuss
using Blackline Master “Subtracting Decimals.” Students
Homework                           should finish any remaining problems and the journal prompt
   Finish “Subtracting Decimals”                  for homework.
   “Subtracting Decimals Journal Prompt”

Vocabulary
Ungroup: To break into a new group in             Source: Teacher Created – Find the Missing Decimal
order to subtract. For example, 1 hundred         Number activity adapted from Math Expressions
can be ungrouped into 10 tens.

Wake County Public School System, 2012
Transparency/Blackline Master   Grade 5   Day 32   Standard 5.NBT.7

Name: ________________________
Date: ________________________

Problem Solving with Decimals
Incorrect Change
Aiden purchased a book for \$8.56 at the local bookstore with a
\$10 bill. The cashier gave her \$2.56 in change. Aiden told the
cashier to check her math again. What did the cashier do
wrong?

Distance Traveled
Kenneth drove 35.95 miles to his grandmother’s house. His
cousin Billy drove 63.1 miles to meet him there. How much
farther did Billy drive than Kenneth?

Wake County Public School System, 2012
Transparency/Blackline Master   Grade 5   Day 32   Standard 5.NBT.7

Name: ________________________
Date: ________________________

Find the Missing Decimal Number
1. Copy the missing number problems below onto your
MathBoard.

8.17                             5.76
– ____                           – ____
4.38                             2.9

2. Work together to find the missing numbers.

3. By yourself, write three missing number problems on
solve.

Wake County Public School System, 2012

Problem Solving with Decimals

Incorrect Change: \$10.00 – \$8.56 = \$1.44

Distance Traveled: 63.1 – 35.95 = 27.15 miles

Find the Missing Decimal Number

8.17                            5.76
– 3.79                          – 2.86
4.38                            2.9

Wake County Public School System, 2012
Blackline Master   Grade 5   Day 32   Standard 5.NBT.7

Name: ________________________
Date: ________________________

Subtracting Decimals
Directions: Solve the following problems. Use estimation to determine if your answers
make sense.

1. 4.57 – 2.9 = _______                                   2. 1.67 – 0.28 = _______

3. 25.7 – 1.65 = _______                                  4. 34 – 15.34 = _______

5. 93.1 – 77 = _______                                    6. 59.26 – 42.7 = _______

7. Jacqueline cut 1.53 yards of ribbon from a roll that had 5 yards of ribbon on it. How
many yards of ribbon are left on the roll?

Wake County Public School System, 2012

Subtracting Decimals

1. 4.57 – 2.9 = 1.67                                       2. 1.67 – 0.28 = 1.39

4.57                                                     1.67
– 2.9                                                    – 0.28
1.67                                                     1.39

3. 25.7 – 1.65 = 24.05                                     4. 34 – 15.34 = 18.66

25.7                                                       34
– 1.65                                                    – 15.34
24.05                                                      18.66

5. 93.1 – 77 = 16.1                                        6. 59.26 – 42.7 = 16.56

93.1                                                      59.26
– 77                                                      – 42.7
16.1                                                      16.56

7. Jacqueline cut 1.53 yards of ribbon from a roll that had 5 yards of ribbon on it. How
many yards of ribbon are left on the roll?

5
– 1.53
3.47

Wake County Public School System, 2012
Blackline Master   Grade 5   Day 32   Standard 5.NBT.7

Name: ________________________
Date: ________________________

Subtracting Decimals Journal Prompt

Why is it important to write numbers with the same place value beneath
each other when you are subtracting decimals using a vertical format?
Use appropriate math vocabulary in your explanation.

Wake County Public School System, 2012

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