MAFS.2.NBT.2.7 Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
Cognitive Complexity Level: 2 – Basic Application of Skills and Concepts
[divider] [/divider] Students are able to…
- Solve addition and subtraction problems within 1000 using a variety of strategies including concrete models, pictures, hundreds charts, benchmark numbers, number lines, place value charts, and mental computation.
- Explain strategies (including estimation) to peers for adding and subtracting within 1000 and discuss comparisons with peers’ reasoning.
[divider] [/divider] Students are able to…because teachers:
- Engage students in learning experiences where students model addition and subtraction within 1000 using concrete tools and pictorial models
- Encourage and set expectations for students to explain how their models connect to peer models and written equations.
- Provide students with many opportunities to model addition and subtraction using hundreds chart, place value charts, and open number lines.
- Facilitate conversations among students where students reason through strategies and make connections between a variety of representations for addition and subtraction within 1000.
- Pose questions to elicit student’s mental processes while solving, highlighting mathematical connections.
[divider] [/divider] Questions to ask students:
- Ask: Ask students how could you figure out 502 – 16?
- Sample answer that indicates understanding: “I would count back 2 to 500 and then back 10 more to 490 then 2 more to 488 and back the final 2 landing on the difference 486.” “I would subtract ten first making 492 then I would break 492 into 480 + 12 then I know double 6 is 12 and since I need to subtract 6 I would be left with 486.”
- Sample answer that indicates an incomplete understanding or a misconception: “I’d cross out the 2 and make it 12 and then subtract 6. Then I’d cross out 0 and make it 10 and cross out the 5 and make it 4.”
- Ask: Ask students what strategies could you use to figure out 288 + 637?
- Sample answer that indicates understanding: “I could use an open number line, place value, a concrete or pictorial model”
- Then select a strategy stated and ask student to show the strategy and think aloud as they solve.
- Sample answer that indicates understanding: “I would break each addend up and first add 280 + 630 total 910 then I would add 8 + 7 which is 15. I would join the values together find the sum to be 925.”
- Ask: Ask students to look at an equation they are solving and explain how you know whether regrouping is required.
- Sample answer that indicates understanding: “I have to regroup with this equation because there are not enough tens to subtract so I need to regroup from the hundreds place.”
[divider] [/divider] Additional Resources:
Additional in depth content knowledge
Blog Post: Progression of Addition and Subtraction
Video: Add three digit numbers with base ten blocks
https://learnzillion.com/lesson_plans/5734-add-three-digit-numbers-with-base-ten-blocks
[divider] [/divider] Sample Formative Assessment Tasks:
[divider] [/divider]
Ask: In which year did the players from both leagues hit the most runs?
Ask: How many hits were made in each year by both the National and American League players?
Ask: How many more hits did Charlie Blakmon have in 2017 than Adrian Beltre had in 2013?
[divider] [/divider] Resources/Tasks to Support Your Child at Home:
- Kahn Academy Video: Adding 3-Digit Numbers (no regrouping) https://tinyurl.com/ohku28k
- Kahn Academy Video: Adding & Subtracting on Number Line https://tinyurl.com/yaf6b9ug
- Create 3- digit addition and subtraction equations for your child to solve using virtual base ten blocks or an open number line. Ask them to use math vocabulary to explain each step.
- Task: Ricky was playing a basketball video game with his friend. Ricky scored 125 points. His friends scored 98 points. How many points did they score altogether? Use a quick pic to show your thinking.
- Task: Choose a strategy to solve 640-239.