MATH · GRADES 6-8 · 30-35 MIN
Below Zero: Integers on a Two-Way Number Line lesson plan
Students walk integer addition and subtraction on a two-way number line and explain subtracting a negative as a direction reversal.
At a glance
Time: 30-35 min
Grades: Grades 6-8
Subject: Math: Integers on a Two-Way Number Line
Grouping: Pairs.
Space: A straight line of at least 20 ft.
Teacher prep: 10 min printing + 15 min taping
Included: Teacher guide, student sheet, checks for understanding, exit ticket with answers
Open the printable lesson: teacher guide and student sheet →
Essential question
Why does subtracting a negative move you forward?
What students learn and show
Learn: Adding a negative moves left; subtracting a negative is equivalent to adding its opposite.
Show: Solve integer addition and subtraction and explain why subtracting a negative increases a value.
Objectives
Locate positive and negative integers on a scaled line
Model integer addition and subtraction by walking
Explain subtracting a negative as a direction reversal
Compare integers using position (left is less)
Before this lesson students should: Integers on a number line (6.NS.C.6).
Materials and prep
The 1:1 print (a long hallway)
Painter's tape
Integer cards
Pencils
Prep (about 10 min to print, 15 min to tape)
Tape 0 in the middle of a hallway and mark integers each way.
Agree the facing/walking rules.
Space: A straight line of at least 20 ft.
Grouping: Pairs.
Ways to run it: Painter's tape on the floor; 1:1 printed floor plan; real
Lesson procedure
Teacher model: '3 + (-5): face positive, walk backward 5: -2. 2 - (-4): face negative (subtract), walk backward 4 (negative number): you move toward positive: 6.'
Guided practice: Pairs walk 4 + (-3) and -1 - (-2) with a partner checking.
Build the line: tape and label integers both directions from zero.
Addition walks: start at 3, 'add negative 5' — face positive, walk backward 5 — land on -2. Walk several.
The tricky one: start at 2, 'subtract negative 4.' Subtract = face negative; the -4 = walk backward — and backward-while-facing-negative is toward positive. Land on 6. Feel why two negatives turned positive.
Compare: two students on the line — the one to the left is always less, even at -8 vs -3.
Real context: temperature or elevation — walk a story ('it was 5 below, rose 8 degrees') and read the result off the floor.
Checks for understanding
Ask: Start at 3, add -5. Where do you land? Look for: -2.
Ask: Start at 2, subtract -4. Where do you land? Look for: 6.
Ask: Which is less, -8 or -3? Look for: -8.
Exit ticket
-3 + 7 = ? Answer: 4.
5 - (-2) = ? Explain. Answer: 7; subtracting -2 is the same as adding 2.
-6 - 3 = ? Answer: -9.
Scoring: 1 point each. Item 2 needs the explanation.
Common misconception
Students may think: Two negatives always make a positive.
Address it: That rule is for multiplication; -3 + (-2) = -5.
Supports and extensions
Learning support: Addition only first; the physical turn-and-walk removes the abstraction; number line pre-marked.
Multilingual learners: Direction is the whole idea; 'positive/negative,' 'more/less' shown by position and facing.
Mobility and access: Integer moves can be made with a token on a desk number line; reasoning stays the goal.
Extension: Multiply: what would 'negative 2 times 3' look like as a walk — and why does the answer face backward?
Transfer task: Temperature was -4 degrees and rose 9 degrees. New temperature?
Spaced review: Two weeks later: -7 - (-10).
Standards connections
CCSS 6.NS.C.6 (standard)
CCSS 7.NS.A.1 (standard)
Connections show which skills the activity practices. They are not a claim of full coverage; see the library for scope notes.
Why this approach
A 10-week program delivered by classroom teachers to 337 students in grades 3-6 (15 classes) improved spatial reasoning relative to standard mathematics instruction. Limit: The study measured spatial reasoning only, not mathematics achievement, and did not test this lesson.
Ready to teach it?
The printable version has the full teacher guide, a student recording sheet, prep steps and an exit ticket. Open the printable lesson →
Need the floor plan itself? Get a 1:1 print quote.
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