Stretch: Choosing the Sign and the Zero
I can use positive and negative numbers to model real situations and explain what zero represents.
🧠 The Challenge
positive / negativeopposite quantitieszero pointelevation / temperature / money
Signed numbers describe quantities with opposite directions. You choose where zero is (sea level, freezing, break-even), then one direction is positive and the other negative.
👀 Worked Example
A submarine 40 m below sea level is −40 (zero = sea level). A $25 deposit is +25; a $25 charge is −25. A gain of 5 then a loss of 5 returns you to 0.
✏️ Your Turn
0 of 3 checks complete
1. A bank account: a withdrawal of $30 is best written as…
2. If +8 means 8°C above freezing, what does −3 mean?
3. A diver rises from −20 m to −5 m. The change is…
💬 Explain Your Thinking
Describe a real situation and how you'd use signed numbers for it:
"In my situation, zero means blank. Positive means blank and negative means blank. Example value: blank."