Activity 01
Pairs: Strategy Swap Game
Partners draw problem cards like 56 + 37. One solves mentally, explains the strategy used, such as making tens. Switch roles after three problems and compare methods. End with partners creating their own problem.
How does making a ten or hundred make addition easier?
Facilitation TipDuring Strategy Swap Game, circulate and listen for pairs to name the strategy they just used, not just the answer.
What to look forPresent students with a series of addition and subtraction problems (e.g., 58 + 7, 92 - 19). Ask them to write down the strategy they used for each problem (e.g., 'making tens', 'compensation', 'known facts') and their answer.
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Activity 02
Small Groups: Compensation Hunt
Provide cards with addition problems suited for compensation. Groups sort them into 'easy to compensate' and 'other strategies,' solve each, and justify choices. Share one group example with the class.
What is the compensation strategy, and when is it useful?
Facilitation TipDuring Compensation Hunt, provide mini whiteboards so students can record both the adjusted and final numbers.
What to look forPose the problem: 'Sarah has 35 stickers and buys 18 more. How many does she have now?' Ask students to share how they would solve this mentally. Prompt them with: 'Could you use compensation? How would that work? What if you made a ten instead?'
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Activity 03
Whole Class: Mental Math Number Talk
Pose problems like 81 - 29 on the board. Students use signals to share strategies silently, then volunteers explain aloud. Record multiple methods on chart paper for reference.
How can we use known addition facts to solve subtraction problems mentally?
Facilitation TipDuring Mental Math Number Talk, record all student ideas on the board, even if some are less efficient, to show thinking diversity.
What to look forGive each student a card with a problem like '63 - 27'. Ask them to write the answer and then explain in one sentence how they found it using a mental math strategy.
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Activity 04
Individual: Strategy Journal Reflection
Students solve five mixed problems mentally, note the strategy chosen and why. Draw quick sketches if needed, like tens frames. Share one entry with a partner.
How does making a ten or hundred make addition easier?
What to look forPresent students with a series of addition and subtraction problems (e.g., 58 + 7, 92 - 19). Ask them to write down the strategy they used for each problem (e.g., 'making tens', 'compensation', 'known facts') and their answer.
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Generate Complete Lesson→A few notes on teaching this unit
Start with the simplest strategy, making tens, because it reduces cognitive load. Avoid teaching written-column language like ‘carry’ or ‘borrow’ as it can anchor students to paper methods. Research shows that students who verbalize their steps develop stronger number sense than those who only compute silently.
Students will select and use at least two different mental strategies for each problem and explain their choice to a partner. They will demonstrate speed and accuracy without relying on written steps or counting on fingers.
Watch Out for These Misconceptions
During Strategy Swap Game, watch for students who always add ones first instead of making tens.
Prompt pairs to test both ways and time themselves to see which method finishes first, then discuss why making tens is faster.
During Compensation Hunt, watch for students who only adjust numbers that end in 9 or 1.
Ask groups to adjust their sorting rules and find three examples where they add or subtract 2, 3, or other numbers to build broader understanding.
During Mental Math Number Talk, watch for students who immediately count back when subtracting.
Highlight the connection between subtraction and addition by asking, 'What do you already know that can help you solve this?' and recording their related addition facts on the board.
Methods used in this brief