Negative Numbers: Travel Across Zero
Understand that numbers below zero are negative, that lower on the number line always means smaller, and that the opposite of a number and its absolute value describe distance from zero.
Before you try
What if it was −7 degrees outside and 3 degrees inside? Which is colder, and by how much?
Try it out
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What happened?
Move a control to see what changes and why.
The line shows whole numbers at fixed steps. Real quantities can sit anywhere between them.
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Try these ideas
- Set A to −7 and B to 3, then read the difference B − A.
- Switch to elevation and put a marker below sea level.
- Press Land on the target and reach it in the fewest moves.
Why it works
A number line does not stop at zero. Below zero the numbers keep going, marked with a minus sign, and the further down you go the smaller the number gets. That is why −7 is colder than 3, even though the digit 7 is bigger than 3. Lower on the line always means smaller, whatever the digits look like.
Two other ideas go with this. The opposite of a number is the same distance from zero on the other side, so the opposite of −7 is 7. The absolute value, written with two bars, is just the distance from zero and is never negative, because a distance cannot be. In this simulator you set two values, read the comparison, the opposite, the absolute value and the difference, and use move buttons to travel across zero.
Check your understanding
Question 1 of 4
Which is the colder temperature, −7 °C or 3 °C?
What is the opposite of −4?
What is the absolute value of −9?
A submarine at −30 m rises 18 m. Where is it now?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Look at a weather forecast for a cold country and order the temperatures.
- Ask what a bank balance of −500 rupees would mean.
- Count down and past zero on a lift with basement floors.