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Ratios and Data 6-8 / Week 07 / Wednesday
3/6
Week 07 · Adding and Subtracting Signed Numbers

Wednesday

Numbers Lab: the floor number line
// Hops on the number line
⏱ about 20 min

Wednesday: Numbers Lab, the Floor Number Line

Rocket unrolls a strip of masking tape down the hallway. "A number line we can walk on. Zero goes by the door."

Raven marks the tape every big step, from -6 to 6, with a marker. "What do you notice about the zero mark?"

"It is the only one with no sign," Rocket says. "Left is negative, right is positive."

Nova hovers at the zero mark, her light pointing straight down. "Someone call a problem," she says.

Raven reads from the Numbers Desk notebook. "Start at -2. Add 5."

Rocket steps to -2, faces the positive end and takes five steps. "3!"

"Now subtract 4," Raven says. Rocket turns to face the negative end and walks four steps. "-1."

Nova dims her light. "Write every walk down. The data tell the story."

What you need

  • Masking tape, about 4 big steps long, on a clear hallway or room floor.
  • A marker to write the numbers -6 to 6 on the tape.
  • Your Numbers Notebook and a pencil.
  • A partner to call out problems (a family member works well).
Safety first
Clear the floor first: no toys, cords or rugs that slide. Wear shoes or grippy socks.
Walk the hops, never run or jump. Face the way you are hopping.
A grown-up says yes to the tape spot and helps peel it up afterward.

Build and walk

  1. Tape a straight line on the floor. Mark 0 in the middle, then one mark per big step both ways.
  2. Write the positive numbers to the right of 0 and the negative numbers to the left.
  3. Your partner calls a start number and a hop, like "start at -2, add 5".
  4. Stand on the start number. Face the positive end to add a positive number or subtract a negative one.
  5. Face the negative end to add a negative number or subtract a positive one. Walk the hops.
  6. Record the start, the hop and the landing number in your table. Do at least eight walks.

The crew's walks

Here is the crew's table from the hallway. Every walk is written as a number sentence.

WalkStartHop calledNumber sentenceLanded on
1-2add 5-2 + 53
23subtract 43 - 4-1
3-1subtract -3-1 - (-3)2
42add -62 + (-6)-4
5-4add -2-4 + (-2)-6
6-6subtract -6-6 - (-6)0
CHECK THE CREW'S WALKS
  • Read the question.
  • Tap your answer.
Walk 3: start at -1 and subtract -3. Where did Rocket land?
Walk 4: start at 2 and add -6. Where did Raven land?
Walk 6: start at -6 and subtract -6. Where did Rocket land?
WHICH WAY TO FACE?
  • Read the question.
  • Tap your answer.
You are adding a negative number. Which end do you face?
You are subtracting a negative number. Which end do you face?
You are subtracting a positive number. Which end do you face?
WALKS THAT CROSS ZERO
  • Read the question.
  • Tap your answer.
Walk 1: start at -2 and add 5. Where did Rocket land?
Walk 5: start at -4 and add -2. Where did Raven land?
Which walk landed below zero after starting above it? Start at 3 and subtract 4.
Walk 2 started at 3 and subtracted 4. Where did Raven land? Type the number.
WHY THIS EXERCISEA walk that crosses zero is the one most people get wrong. The floor line makes it clear.
Draw your floor number line from -6 to 6. Mark your favorite walk with arrows for each step.

Great lab work. Your feet now know the rules. Tomorrow you read Raven's thermometer log and find every change.

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