# q1-day31-subdecimals by JuyeeDasNair

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```									                             Mathematics Alignment Lesson
Grade 5 Quarter 1 Day 31
Common Core State Standard(s)                                           Alignment Lesson
5.NBT.7 Add, subtract, multiply, and divide                        Subtracting Decimals Using Models
decimals to hundredths, using concrete models or
1. Display Transparency/Blackline Master, “Subtracting
drawings and strategies based on place value,
properties of operations, and/or the relationship      Decimals Using Models 1”. Present Scenario 1 to students
between addition and subtraction; relate the           and ask them to use what they know about decimals to
strategy to a written method and explain the           estimate the number of feet Colin will need to cut from the
reasoning used.                                        package of border. Discuss the subtraction sentence
represented by the problem. Write the sentence horizontally
Standards for Mathematical Practice                 on the board (4.5 – 3.8). Ask students how they might use
Standard 2- Reason abstractly and                      base ten blocks to find the solution.
quantitatively.                         2. Model how to use base ten blocks to subtract the decimals.
Standard 4- Model with mathematics.                    Start with a base ten model of the larger number. Take away
Standard 5- Use appropriate tools                      three wholes. Then, teach students to “ungroup” the
strategically.                            remaining whole so they will be able to take away the eight
tenths, leaving them with seven tenths. Compare the answer
Materials Needed:                          to the class estimate.
   Base Ten Blocks for each student (flats,        3. Present Scenario 2 to students and have students work in pairs
rods, units)                                   to find a solution, using the same four steps you modeled.
   Blackline Masters- “ Subtracting                4. Use Math Talk to have pairs of students share solutions. Be
Decimals with Base Ten Grids”,                 sure to include discussion about place value and ungrouping.
”Subtracting Decimals Using               5. Display Transparency/Blackline Master, “Subtracting
Models Journal Prompt”,                  Decimals Using Models 2”. Present Scenario 3 to students
”Blank Base Ten Grids”                 and have students work independently to find a solution using
   Transparencies/Blackline Masters-                  the same four steps.
“Subtracting Decimals Using Models            6. Use Math Talk to have students share solutions. As students
1”, “Subtracting Decimals Using              share solutions, have them attempt to draw the base ten
Models 2”, “Subtracting                  representations on the board. This will help make the
Decimals Using Models 3”               connection to subtracting using base ten grids on paper.
7. Display Transparency/Blackline Master, “Subtracting
Decimals Using Models 3”. Present Scenario 4 to students
Assessment
and estimate the difference in the heights. Write the
Informal:
horizontal subtraction sentence that represents the problem,
 Assess student solution strategies and
and ask how students might use base ten grids on paper to find
discussion during partner work,
independent work, and math talk.
 Journal Prompt explanation                        8. Model how to shade the larger number on the base ten grids
first. Then, break the smaller number into tenths and
hundredths, and show the subtraction of each part using a line
Homework                              to cross out the tenths and x’s to cross out the hundredths.
   Finish “Subtracting Decimals with Base             Compare the resulting answer to the class estimate.
Ten Grids”
9. Use the remaining time for students to practice and discuss
   “Subtracting Decimals Using Models                 using Blackline Master “Subtracting Decimals with Base Ten
Journal Prompt”                                    Grids.” Students should finish any remaining problems and
the journal prompt for homework.
Vocabulary                         Note: An extra page of grids has been included in this lesson to be
Ungroup: To break into a new group in               used for additional practice as needed.
order to subtract. For example, 1 hundred
can be ungrouped into 10 tens.                                                      Source: Teacher Created

Wake County Public School System, 2012
Transparency/Blackline Master   Grade 5   Day 31   Standard 5.NBT.7

Name: ________________________
Date: ________________________

Subtracting Decimals Using Models 1
Scenario 1
Colin bought a package that has 4.5 feet of border for his
science project display. He needs 3.8 feet of border. How
many feet of border will Colin need to cut from the original
package of border?

Scenario 2
Jasmine and Eunice built model cars to study force and motion.
Jasmine’s car traveled 2.3 meters. Eunice’s car traveled 1.95
meters. How much farther did Jasmine’s car travel?

Remember to:
2. Write a horizontal problem to represent the scenario.
3. Use base ten blocks to find a solution.

Wake County Public School System, 2012
Transparency/Blackline Master   Grade 5   Day 31   Standard 5.NBT.7

Subtracting Decimals Using Models 2
Scenario 3
Jason bought a candy bar from the store for \$0.79. He gave the
clerk a \$5 bill to pay for the candy bar. How much change will

Remember to:
2. Write a horizontal problem to represent the scenario.
3. Use base ten blocks to find a solution.

Wake County Public School System, 2012
Transparency/Blackline Master   Grade 5   Day 31   Standard 5.NBT.7

Subtracting Decimals Using Models 3
Scenario 4
Elizabeth is 1.3 meters tall. Her little brother, David, is 0.78
meters tall. How much taller is Elizabeth than David?

Wake County Public School System, 2012

Subtracting Decimals Using Models
Scenario 1: 4.5 – 3.8 = 0.7 feet
Model with Base Ten Blocks: Begin with 4 flats and 5 rods. Take
away 3 flats. “Ungroup” the remaining flat by trading it for 10 rods.
Take away 8 rods. The result is 7 rods.

Scenario 2: 2.3 – 1.95 = 0.35 meters
Model with Base Ten Blocks: Begin with 2 flats and 3 rods. Take
away 1 flat. “Ungroup” the remaining flat by trading it for 10 rods.
Take away 9 rods. There are now 4 rods. “Ungroup” one rod by
trading it for 10 units. Take away 5 units. The result is 3 rods and 5
units.

Scenario 3: \$5 – \$0.79 = \$4.21
Model with Base Ten Blocks: Begin with 5 flats. “Ungroup” one flat
by trading it for 10 rods. Take away 7 rods. There are now 4 flats
and 3 rods. “Ungroup” one rod by trading it for 10 units. Take away
9 units. The result is 4 flats, 2 rods, and 1 unit.

Scenario 4: 1.3 – 0.78 = 0.52 meters
Shade on Base Ten Grid: First, shade one whole and three tenths (3
columns). Then, cross out 7 tenths by drawing a line through 7 of the
shaded columns. Cross out 8 hundredths by drawing an “x” on 8
small boxes in the next column. The result is 5 tenths, and 2
hundredths.

Wake County Public School System, 2012
Blackline Master    Grade 5   Day 31   Standard 5.NBT.7

Name: ________________________
Date: ________________________

Subtracting Decimals with Base Ten Grids
1. 0.85 – 0.69 = _______                    2. 1.64 – 0.9 = _______

3. 1.5 – 0.63 = _______                                            4. 1 – 0.72 = _______

5. 2.89 – 1.97 = _______

Wake County Public School System, 2012

Subtracting Decimals with Base Ten Grids
1. 0.85 – 0.69 = 0.16                    2. 1.64 – 0.9 = 0.74

3. 1.5 – 0.63 = 0.87                                              4. 1 – 0.72 = 0.28

5. 2.89 – 1.97 = 0.92

Wake County Public School System, 2012
Blackline Master   Grade 5   Day 31   Standard 5.NBT.7

Name: ________________________
Date: ________________________

Subtracting Decimals Using Models Journal Prompt

Explain how you would use base ten blocks to solve the problem 1.85 –
0.97. Use appropriate math vocabulary in your explanation.

Wake County Public School System, 2012
Blackline Master   Grade 5   Day 31   Standard 5.NBT.7

Blank Base Ten Grids for Extra Practice

Wake County Public School System, 2012

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