Solve the Story Problem

Overview

Students will use drawings, bar models, manipulatives, and equations to solve one- and two-step addition and subtraction word problems within 100. The lesson builds on familiar fact strategies by helping students identify the situation, locate the unknown, choose an operation, and explain how their equation matches the story.

Learning intentions

Students will be able to:

• Represent addition and subtraction situations with drawings, bar models, or manipulatives.
• Solve one- and two-step word problems within 100.
• Write equations using a symbol for an unknown number.
• Explain how an equation matches the quantities and actions in a problem.

Success criteria

• I can identify what is known and what is unknown.
• I can show the problem with a drawing, bar model, or manipulatives.
• I can choose addition or subtraction and solve accurately.
• I can explain how my equation matches the story.

Curriculum links

• Operations and Algebraic Thinking — addition and subtraction word problems within 100, including unknowns in all positions.
• Operations and Algebraic Thinking — fluent addition and subtraction within 20 using mental strategies.
• Number and Operations in Base Ten — place-value strategies for adding and subtracting within 1,000.

Lesson structure (60 minutes)

1. 0–5 min · Hook and activate prior knowledge. Open with the mystery story hook and display: “There are 28 books on a shelf. Some more are added. Now there are 45. How many were added?” Students use a quick sketch or mental strategy, then turn and explain what the unknown represents. Briefly review addition, subtraction, and related fact families within 20.

2. 5–15 min · Model the problem-solving routine. Use the problem-solving routine slides to model: read the story, identify known and unknown quantities, represent the situation, write an equation, solve, and check. Think aloud while solving “Mia has 36 stickers. She gives 14 away. How many stickers does she have left?” Build a bar model and write (36 - 14 = s), then explain that (s) stands for the unknown stickers left. Students help identify the action and repeat the routine using gestures: read, show, equation, solve, explain.

3. 15–25 min · Guided practice with varied unknowns. Display the three problems on the guided practice problems one at a time. Solve together using connecting cubes, drawings, or bar models:

• Add to, result unknown: “There are 27 birds. 18 more arrive. How many birds are there now?”
• Take from, start unknown: “Some crayons were in a box. 16 were used. There are 32 left. How many were in the box?”
• Compare, difference unknown: “Jamal has 54 points. Ana has 39 points. How many more points does Jamal have?” For each, ask, “What does the unknown mean?” and “How does the equation match the story?” Check answers with turn-and-talks and mini-whiteboards.

4. 25–37 min · Partner practice. Pair students strategically and distribute the word-problem practice sheet. Partners take turns as Reader and Explainer, switching roles after each problem. They solve four problems involving put together, take apart, compare, and a two-step situation. For every problem, students must show a representation, write an equation with a symbol such as (n), and write or say one explanation. Circulate and ask: “What does your symbol stand for?” “Which numbers belong in the first step?” “How do you know your operation makes sense?”

5. 37–49 min · Independent practice. Students complete the remaining problems on the independent practice section independently. Include one problem for each unknown position and one two-step problem, such as: “The class collected 24 cans on Monday and 19 on Tuesday. They gave 15 cans to a food bank. How many cans remained?” Require a drawing, bar model, or labeled quantities and an equation for each step. Students who finish early create a new word problem with a start-unknown or compare situation and solve it.

6. 49–55 min · Share, compare, and address errors. Use the discussion and error-analysis slides to show two sample representations for the same problem, including one with a misplaced operation. Students compare them with a partner and explain which representation matches the story. Invite two students to share different valid strategies, such as a number line and decomposing by tens and ones. Emphasize that a correct answer must be connected to the situation.

7. 55–60 min · Exit ticket and reflection. Students complete the exit ticket at the bottom of the exit ticket section: “Lena has 23 shells. She finds some more and now has 41. How many shells did she find?” Students draw or make a bar model, write an equation using (s), solve, and complete: “My equation matches because….” Collect responses to group students for the next lesson.

Resources

• the complete word-problem slide deck
• the word-problem practice sheet
• Connecting cubes or counters
• Mini-whiteboards, markers, and erasers
• Pencils and crayons
• Chart paper or board space
• Prepared partner roles: Reader and Explainer

Assessment

• During modeling and guided practice, check whether students identify the unknown, select a suitable operation, and connect the equation to the story.
• Review whiteboard responses and circulate during partner and independent work, recording students who need support with unknown positions or two-step problems.
• Use the exit ticket to assess representation, equation writing, calculation, and explanation. A complete response includes (23 + s = 41), (s = 18), and a matching explanation.

Differentiation

• Support students with counters, pre-drawn bar-model templates, number lines, and a routine card: “I know ___; I need to find ___; I will ___.” Read problems aloud and clarify vocabulary such as more, fewer, left, total, and difference.
• Provide a small teacher-led group during independent practice. Begin with result-unknown problems and use numbers within 50 before moving to start-unknown, compare, and two-step problems.
• For EAL students, pair each problem with a quick sketch and sentence frames: “The unknown is ___.” “I used ___ because the story says ___.” Allow students to explain orally before writing.
• Extend ready students by asking them to solve one problem in two ways, write a second equation that represents the same situation, or create a two-step problem with a specified answer.