LESSON PLAN

Symbolic Equality and Inequality

Apothem Team

Grade 2 · Number

LESSON AT A GLANCE

Warm-up

5 min

Explore

15 min

Consolidate

10 min

Practice

12 min

Exit ticket

3 min

Warm-up

True or false? Show 4 sentences rapidly: 40 + 32 = 42 + 30 (true); 56 - 20 = 56 - 22 (false); 35 + 40 = 30 + 45 (true); 67 + 0 = 67 (true). Students show thumbs up or down. Discuss one that surprised the class.

Explore

Relational thinking challenge cards: each card shows an equation with one value missing. 53 + 24 = 54 + ?. Students solve WITHOUT adding either side. Write the reasoning: 54 is 1 more than 53, so the second addend must be 1 less: 23. Verify by computing if uncertain.

Consolidate

Practice

Students sort 10 number sentences into TRUE and FALSE, recording reasoning for each. Solve 4 relational thinking problems without computing both sides. Exit ticket: 44 + 19 = 45 + ?, find the missing number without adding.

Exit ticket

TIP When a student correctly identifies a sentence as true or false, always ask how do you know? The explanation reveals whether they computed or reasoned relationally. Both are valid; celebrate both but name the relational approach explicitly.

WORKED EXAMPLES

Solve without computing both sides: 36 + 25 = 37 + ?

37 is 1 more than 36. To keep the total the same, the second addend must be 1 less than 25: 24. So ? = 24. Verify: 36+25=61, 37+24=61. Correct.

Is 73 - 38 = 75 - 40 true?

73 to 75: add 2. 38 to 40: add 2. Both numbers increased by 2, so the difference is unchanged. TRUE. This is the equal-differences pattern for subtraction.

MATERIALS

•Pan balance

•True/False sort cards with two-digit expressions

•Relational thinking task cards

•Student whiteboards

WATCH FOR

!Students may compute both sides every time even when relational thinking is faster. Actively reward relational thinking: ask who solved this without computing? and give that student the first explanation opportunity.

!Students may think changing both sides always preserves equality. It depends on the operation: adding the same to both addends of an addition changes the sum; subtracting the same from both preserves the difference.