L1 · Positive and negative numbers in real life

Learning goal

“I can write a positive or negative number for a real-life situation - temperature, debt, and elevation - and I can say what the number means, using zero as the reference point.”

Positive number — a number greater than zero, like 5 or +5. Gains, above, and forward are usually positive.

Negative number — a number less than zero, written with a - sign, like -3. Losses, below, and owing are usually negative.

Zero (the reference point) — the starting line a signed number is measured from: 0°C, sea level, a $0 balance, ground floor.

Integer — a whole number that can be positive, negative, or zero: ..., -2, -1, 0, 1, 2, ...

Worked example

Reading temperatures as signed numbers. Step 1: Zero is the reference point. On a thermometer, 0°C is where water freezes. Step 2: Above zero is positive: 7°C above zero is written 7 (or +7). Step 3: Below zero is negative: 4°C below zero is written -4. The - sign is not decoration - it tells us which side of zero we are on. Model both ways, side by side: a thermometer with 7 and -4 marked, AND a vertical number line from -10 to 10 with both points plotted. The sign tells the direction from zero; the number tells how far from zero.

Check yourself — explain it

Why does '4 degrees below zero' need the - sign?

Paired problem — example still visible

Write 9 degrees below zero as a signed number: -9

Faded completion — last step is yours

"Zero is the reference point. 12 degrees above zero is written 12. One degree below zero is written ___." -> -1

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

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