Counting forwards and backwards
Count forwards and backwards in steps of 3 from 0
What a learner can do afterwards
- Count 3, 6, 9, 12, 15 … up to at least 30
- Count backwards in 3s from 30
- Identify the next number in a sequence of multiples of 3
1 · Read
You already know how to count by 2s. Counting by 3s works the same way, except you add 3 each time instead of 2. Start at 0: 0, 3, 6, 9, 12, and keep going. Every number you land on is called a multiple of three.
Zara stacks blocks in towers of three. She counts the towers: 3, 6, 9, 12. She has four towers, twelve blocks in all.
To count backward by 3s, do the opposite: take away 3 each time instead of adding it. If you lose track, count forward by 3s until you reach your starting number, then say the numbers back in reverse.
Add 3 to count forward, take away 3 to count backward: 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30.
More to read
1.1: Introduction to Whole Numbers (Part 1)
Whole numbers count real things: zero, one, two, and on without end. Each place is ten times its neighbor, so 30 is three tens and 300 is three hundreds. Reading numbers aloud in groups keeps big counts friendly. Order on the number line shows which count is greater. Skip counting hops along that line in equal jumps.
1.2: Introduction to Whole Numbers (Part 2)
Whole numbers count real things: zero, one, two, and on without end. Each place is ten times its neighbor, so 30 is three tens and 300 is three hundreds. Reading numbers aloud in groups keeps big counts friendly. Order on the number line shows which count is greater. Skip counting hops along that line in equal jumps.
Intro to place value: FAQ
Place value gives every digit a job based on where it stands. In 53, the 5 means five tens and the 3 means three ones. Tens blocks and ones cubes make this easy to see and touch. Once you read numbers as tens plus ones, adding and subtracting turn into small steps. Adding ten changes only the tens digit.
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2 · Watch
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Where it sits
Learn first
This opens up
18 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.