Mathematics · 2nd Grade

Active learning ideas

Addition and Subtraction Strategies within 100

Active learning helps students move beyond memorized procedures by letting them test strategies in real time. This topic requires flexibility, not just speed, so students need repeated chances to compare methods and see why one might work better for certain numbers. Student-to-student talk and hands-on tools turn abstract ideas like place value and compensation into something they can manipulate and discuss.

• Common Core State Standards
• CCSS.Math.Content.2.NBT.B.5

• 20–45 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: Strategy Showdown

Present one two-digit addition problem to the class (e.g., 38 + 47). Students solve it individually using any strategy. Partners compare strategies side by side, name each strategy, and decide which was more efficient for these specific numbers. Three pairs share to build a class list of strategy names and when each works best.

Compare different strategies for adding two-digit numbers, such as breaking apart and compensation.

Facilitation Tip

During Strategy Showdown, ask each pair to prepare a 15-second explanation of their chosen method before sharing with the group.

What to look for

Present students with the problem 53 + 28. Ask them to solve it using two different strategies and write one sentence explaining which strategy they found more efficient and why.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 02

• Inquiry Circle
• 35 min · Small Groups

Inquiry Circle: 100 Ways to Get There

Groups are given a target sum (e.g., 75). They must find at least four different addition equations that reach that target, using four different strategies. Groups post their equations and strategies on chart paper. The class identifies which strategy appeared most across groups.

Explain how the commutative property of addition can make problems easier to solve.

Facilitation Tip

During 100 Ways to Get There, circulate and ask guiding questions like, 'What would happen if you adjusted the larger number instead?' to push flexible thinking.

What to look for

Pose the subtraction problem 72 - 35. Ask students to share how they would solve it. Facilitate a discussion comparing strategies like counting up on an open number line versus subtracting by place value. Ask: 'Which strategy feels easiest for these specific numbers?'

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Activity 03

• Stations Rotation
• 45 min · Small Groups

Stations Rotation: Strategy Stations

Four stations each feature one strategy: place value decomposition, compensation, counting up on a number line, and using fact families. Students solve two problems at each station using that station's assigned strategy, then rate how efficient they found it for those specific numbers on a 1-3 scale.

Assess the efficiency of various subtraction strategies for different types of problems.

Facilitation Tip

During Strategy Stations, set a timer so students rotate every 6 minutes, forcing them to adapt their approach quickly to new constraints.

What to look for

Write the problem 45 + 32 on the board. Ask students to show you their answer using a thumbs up if they used place value decomposition, thumbs sideways if they used compensation, and thumbs down if they used another strategy. Then, ask a few students to briefly explain their method.

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

A few notes on teaching this unit

Teach this topic by contrasting strategies side by side so students notice efficiency differences. Avoid rushing to the algorithm; anchor every new method to concrete tools like base-ten blocks or number lines first. Research shows that students who explain their reasoning to peers develop deeper understanding and retain strategies longer.

Successful learning looks like students choosing strategies that match the numbers, explaining their choices clearly, and catching their own mistakes as they go. You’ll see them move from counting one by one to using place value, properties, and adjustments with purpose. By the end of these activities, they should be able to justify why they used a particular strategy.

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Watch Out for These Misconceptions

• During Strategy Showdown, watch for students who decompose 53 + 28 into 50 + 20 = 70 and 3 + 8 = 11, then write 81 without regrouping the extra ten.

  Ask them to model the problem with base-ten blocks and recount the tens column after combining the ones. Have them record each step in a T-chart labeled Tens and Ones to make the regrouping visible before they share their answer.

• During 100 Ways to Get There, watch for students who subtract the smaller digit from the larger in 73 - 28, writing 55 or 45 without regrouping.

  Have them build both numbers with blocks and physically remove 28 from 73 to show the difference. Then prompt them to compare 73 - 28 with 28 - 73 on the same mat to highlight the mismatch in results.

• During Strategy Stations, watch for students who adjust both addends in a compensation problem, such as changing 45 + 32 to 50 + 37 by adding 5 to each, then forgetting to subtract the 5 at the end.

  Give them a whiteboard to record each adjustment step and the corresponding change to the sum. Ask a partner to check their final compensation move before they move to the next station.

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Methods used in this brief

• Think-Pair-Share
• Inquiry Circle
• Stations Rotation