Adding and Subtracting Within 100
Adding and Subtracting Within 100
Objectives
Students will learn reasoning strategies for basic addition and subtraction facts, including student-initiated strategies. Students will learn computation strategies based on flexible use of tens, ones, and number facts, including student-initiated strategies. Students will:
- use their understanding of number combinations to develop fluency in the use of basic facts for addition and subtraction.
- develop and use strategies for solving simple story problems.
- develop and use strategies for whole-number computation with a focus on addition and subtraction of one- and two-digit numbers, with and without regrouping.
- use a variety of methods and tools to compute and estimate sums and differences of quantities and conclude the reasonableness of the result.
Essential Questions
How are relationships represented mathematically?
How can mathematics support effective communication?
How can recognizing repetition or regularity assist in solving problems more efficiently?
How is mathematics used to quantify, compare, represent, and model numbers?
What does it mean to estimate or analyze numerical quantities?
What makes a tool and/or strategy appropriate for a given task?
- What makes a tool/strategy appropriate for a given task?
- How are relationships represented mathematically?
Related Unit and Lesson Plans
Related Materials & Resources
The possible inclusion of commercial websites below is not an implied endorsement of their products, which are not free, and are not required for this lesson plan.
- Elementary and Middle School Mathematics: Teaching Developmentally by Van de Walle. Heinemann, 2009.
- Journal for Research in Mathematics Education, 39(2), 153–183. Henry & Brown, 2008.
- http://illuminations.nctm.org
- http://illuminations.nctm.org/ActivityDetail.aspx?ID=75
- http://www.abcya.com/base_ten_fun.htm (interactive games that provide practice with base-ten blocks)
- http://www.abcya.com/base_ten_bingo.htm (base-ten bingo to help students needing extra support)
Formative Assessment
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View
Short-Answer Items:
1. 20 + 8 = _______
2. 38 + 5= _______
Use 2 hops on the open number line to solve:
3. 25 + 6
4. 33 + 9
5. 47 + 8
Solve the problems below. Show your work.
6. 32 + 10 = ______
7. 48 + 10 = ______
8. Draw a set of base-ten blocks that is 10 more than 28.
9. Lilly had 30 pencils. Her friend gave her 10 more. How many pencils does she have now? How do you know?
10. Tommy got 40 balloons for his birthday party. 10 of them popped. How many does he have left? How do you know?
Short-Answer Key:
1. 20 + 8 = 28
2. 38 + 5= 43
Use 2 hops on the open number line to solve:
3. 25 + 6
4. 33 + 9
5. 47 + 8
Solve the problems below. Show your work.
6. 32 + 10 = 42
7. 48 + 10 = 58
8. Draw a set of base-ten blocks that is 10 more than 28.
9. Lilly had 30 pencils. Her friend gave her 10 more. How many pencils does she have now? How do you know?
40 pencils because 30 + 10 = 40 (answers may vary)
10. Tommy got 40 balloons for his birthday party. 10 of them popped. How many does he have left? How do you know?
30 balloons because 40 – 10 = 30 (answers may vary)
Performance Assessment:
Materials:
- Performance Assessment sheet (M-1-2_Performance Assessment.docx)
- open number line
- base-ten blocks
- mini-whiteboards and markers, or paper and pencils
Procedure:
Hand out a copy of the Performance Assessment sheet (M-1-2_Performance Assessment.docx) and additional work tools. Read the story problem aloud. Ask the student to solve the problem using one of the tools provided, to show his/her work, and to write the number sentence.
“Mr. Paws the dog has 50 bones. He finds 10 more bones buried in the yard. Then Mrs. Whiskers the cat steals 20 bones. How many bones does Mr. Paws have now?”
The student should show his/her work and explain how s/he solved the problem.
Performance Assessment Answer Key and Scoring Rubric:
Possible responses may include:
Mr. Paws has 40 bones.
50 + 10 = 60
60 – 20 = 40, or 60 – 10 – 10 = 40
Points
Description
4
- Model of work is clear and accurate.
- Verbal explanations are thorough, detailed, and clear.
- Student displays excellent understanding of the questions, mathematical concepts, and processes.
- Student performs beyond the problem requirements and possibly demonstrates multiple methods or solutions.
- Written number sentence is accurate.
3
- Model of work is clear and accurate.
- Verbal explanations are thorough.
- Student displays appropriate understanding of the questions, mathematical concepts, and processes.
- Written number sentence is accurate.
2
- Model of work is unclear or has minor mistakes.
- Verbal explanations are present but lacking some detail.
- Student displays partial understanding of the questions, mathematical concepts, and processes.
- Written number sentence is inaccurate.
1
- Model of work is unclear and inaccurate.
- Verbal explanations are incomplete and lack detail.
- Student displays little understanding of the questions, mathematical concepts, and processes.
- Written number sentence is inaccurate.
0
- Model of work is not attempted.
- Verbal explanations are illogical or not present.
- Student displays no understanding of the questions, mathematical concepts, and processes.
- Written number sentence is missing.
Final 4/27/14
