Grade 1 · Mathematics
Quarter 2 · Week 6 · TEKS
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This lesson helps first-grade students develop and explain strategies to solve addition and subtraction problems within 20. Students will use spoken words, objects, pictorial models, and number sentences to represent and solve problems. They will also create and solve problem situations based on given number sentences. The lesson supports students in understanding addition and subtraction as related operations and applying multiple representations to deepen their comprehension.
Students should understand the concepts of addition and subtraction as combining and separating groups of objects. They should be familiar with counting numbers up to 20 and recognizing number symbols.
Addition means putting groups together to find the total number, while subtraction means taking away from a group to find what remains. Strategies to solve these problems include using objects (manipulatives), drawing pictures (pictorial models), saying the problem and solution aloud (spoken words), and writing number sentences (equations). For example, to solve 7 + 5, a student might count out 7 counters, then 5 more, and count all to find 12. Or they might draw 7 circles and 5 circles and count the total. Number sentences show this as 7 + 5 = 12.
Encourage students to talk through their thinking. For example, "I had 8 apples, and I got 6 more, so I counted all and got 14 apples." This helps students connect the problem to real situations and clarify their reasoning.
Manipulatives allow students to physically combine or separate groups. Pictorial models, such as drawings of objects or tally marks, help visualize the problem. For subtraction, students can remove objects or cross out pictures. These concrete and visual methods support understanding before moving to abstract number sentences.
Number sentences use symbols to represent addition and subtraction problems, e.g., 15 - 7 = 8. Students learn to write and interpret these sentences as a concise way to show the problem and solution. They also learn to match number sentences to story problems and pictorial models.
Given a number sentence like 9 + 4 = 13, students create a story problem such as "I had 9 balloons, and my friend gave me 4 more. How many balloons do I have now?" Then they solve it using objects, drawings, or number sentences. This deepens understanding by connecting abstract equations to real-life contexts.
Solve the addition problem 8 + 5 using objects and explain your strategy.
The student counts out 8 objects, then counts out 5 more objects, and finally counts all objects together to find the total of 13. They explain, 'I put 8 counters and then 5 more counters, and counted all to get 13.'
I used 8 counters and added 5 more counters. Then I counted all the counters together and got 13.
Given the number sentence 14 - 6 = 8, create a story problem and solve it using a pictorial model.
The student creates a story such as 'I had 14 apples, and I gave away 6. How many apples do I have now?' They draw 14 apples, cross out 6, and count the remaining 8 apples to solve the problem.
I had 14 apples and gave away 6. I drew 14 apples and crossed out 6. I counted 8 apples left, so the answer is 8.
Introduce a simple addition problem within 20 using manipulatives. Model counting objects to find the total and explain your thinking aloud.
Watch the demonstration and then use their own manipulatives to solve a similar addition problem. Share how they solved it using spoken words.
This phase activates prior knowledge about addition and subtraction and introduces the idea of explaining strategies using objects and words.
Provide students with subtraction problems within 20 using pictorial models. Guide them to solve the problems using drawings or objects and explain their strategies.
Work in pairs or small groups to solve subtraction problems using pictures or manipulatives. Discuss and explain their methods to peers.
Students practice solving subtraction problems with concrete and visual tools, reinforcing their understanding and communication of strategies.
Model writing number sentences for addition and subtraction problems solved with objects or pictures. Explain how the number sentence matches the problem and solution.
Write number sentences to represent problems they solved. Explain how the sentence relates to the story or picture.
This phase connects concrete and pictorial representations to symbolic number sentences, helping students understand mathematical notation.
Give students number sentences and ask them to create their own story problems and solve them using objects, pictures, or number sentences.
Generate real-world problems from given number sentences and solve them using strategies learned.
Students apply their understanding by creating and solving problems, demonstrating mastery of concepts and flexibility in thinking.
Ask students to solve an addition or subtraction problem up to 20 using any strategy and explain their thinking orally or in writing.
Solve a problem independently and explain the strategy used to find the answer.
This phase assesses students' ability to apply and communicate their understanding of addition and subtraction strategies.
Work in pairs or small groups to solve subtraction problems using pictures or manipulatives. Discuss and explain their methods to peers.
Use objects to solve 7 + 3. How many objects do you have in total?
Count 7 objects, then add 3 more objects, and count all together to get 10.
Draw a picture to solve 12 - 5. How many are left after you cross out 5?
Draw 12 objects, cross out 5, then count the remaining 7 objects.
Write a number sentence for this story: "I have 9 balloons. I get 6 more balloons. How many balloons do I have now?" Then solve it.
The number sentence is 9 + 6 = 15. The answer is 15 balloons.
Explain how you can use objects, pictures, and number sentences to solve 10 - 4. Which strategy do you find easiest and why?
Using objects, I take away 4 from 10 objects and count what's left. Using pictures, I draw 10 items and cross out 4, then count the rest. Using number sentences, I write 10 - 4 = 6. I find objects easiest because I can physically see and remove items.
Given the number sentence 13 + 7 = 20, create a real-world problem and solve it using any strategy you choose. Explain your thinking.
I had 13 cookies and baked 7 more. How many cookies do I have now? Using objects or drawings, I combine 13 and 7 and count 20. The answer is 20 cookies.
Provide extra manipulatives and step-by-step guidance for students who need concrete support. Use simple story problems with familiar contexts to help understanding. Pair students for peer support during activities.
Use clear, simple language and repeat key vocabulary with visuals. Demonstrate strategies with gestures and objects to support comprehension. Encourage students to use drawings and objects to communicate their thinking.
Challenge students to explain multiple strategies for the same problem. Encourage creating more complex story problems involving addition and subtraction within 20. Have students compare and discuss the efficiency of different strategies.
Ask students to find and solve addition or subtraction problems at home using objects or drawings, then explain their strategies to a family member.
Students learn to solve addition and subtraction problems up to 20 by explaining their strategies using spoken words, objects, pictorial models, and number sentences. They also practice creating and solving problem situations from given number sentences. This builds their understanding of operations and mathematical communication.
Use the exact standards alignment and retrieved-source provenance stored with this enrichment.