Negative Numbers
Count backwards through zero to include negative numbers
What a learner can do afterwards
- Count backwards from 5 through zero: 5, 4, 3, 2, 1, 0, −1, −2 …
- Place negative numbers on a number line
- Understand that negative numbers are less than zero and use them in context (e.g. temperature)
1 · Read
You already know how to count forward: 1, 2, 3, and up and up. Numbers can also go the other way, below zero. When you count down past zero, you reach negative numbers. They have a small minus sign in front, like −1, −2, −3.
Mia checks the temperature before bed. It is 2 degrees. Overnight, it drops 5 degrees. She counts back to find the new temperature: 2, 1, 0, −1, −2, −3. The temperature is now −3 degrees, three degrees below zero.
When you count backward, do not skip over zero. After zero comes negative one, then negative two. Zero itself is the middle point, not a negative number.
Negative numbers are less than zero. Keep counting backward through zero to reach them: 2, 1, 0, −1, −2.
More to read
Intro to negative numbers
Some numbers live below zero. We call them negative numbers and write them with a small minus sign, like -3. Temperatures on frosty days and floors below ground use them every day.
On a number line, negatives sit left of zero. The further left, the smaller and colder the value.
1.1 Introduction to Whole Numbers
Whole numbers are the counting numbers 0, 1, 2, 3 and so on, with no fractions allowed. Each place in a number is worth ten times the place to its right. That is why the 2 in 243 means 200, not just 2.
Place value lets you read, compare and round big numbers. Once you can name the value of each digit, thousands and ten thousands stop looking scary.
1.3 Subtract Whole Numbers
Subtraction takes one number away from another. Stack the numbers with place values lined up and work from the right. When the top digit is too small, exchange one ten from the next column for ten ones.
Check your answer by adding. If the subtraction was correct, the answer plus the number you took away gives back the starting number.
Explore more
2 · Watch
به انگلیسی3 · Play
Walk up and down through zero, one step at a time.
Take it off screen
Where it sits
Learn first
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
17 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.