Human number line for integers: a 25-minute activity, grades 6–8

1. Tape a long line and place the cards in order about a step apart, with 0 in the middle. Ask: "Where would minus 3 degrees go? What about 3 feet below sea level?" Connect each spot to a real context: temperature, elevation, money owed.
2. Comparing: call five students to stand on random numbers. The class orders them least to greatest. Ask: "Is negative 7 greater or less than negative 2? How do you know from where they stand?" The number farther right is always greater.
3. Absolute value: ask two students to stand on 4 and negative 4. "How many steps is each from zero?" Both are 4: absolute value is distance, so it is never negative.
4. Adding: a student starts at 0 facing the positive end. Adding a positive number means walk forward. Adding a negative number means walk backward. Model 3 plus negative 5: three steps forward, five steps backward, land on negative 2.
5. Subtracting: subtraction means turn around to face the negative end, then follow the sign of the second number. For 2 minus negative 4: start at 2, turn around, and walk backward 4 steps, which moves you toward the positive end. Land on 6. Ask: "Why did subtracting make the number bigger?"
6. Rapid rounds: read three problems. Volunteers walk them while seated students predict the landing spot on mini whiteboards or with fingers.

Differentiation: for students who need support, stick to comparing and adding first and save subtraction for day two. For advanced students, add multiplication as repeated moves or have them write their own walking rule for subtraction and test it. For English learners, post positive, negative, greater than, less than and absolute value next to arrows on the line. For students who use wheelchairs or prefer not to walk in front of peers, make the line wide enough to roll along, or let them direct a partner or move a marker on a desk number line.

Quick check: students solve negative 3 minus 5 and negative 3 minus negative 5, and explain the difference in one sentence.

If you try it, tell us how your students explained subtracting a negative in their own words.