Addition and subtraction strategies
Use counting on and counting back as strategies for addition and subtraction
What a learner can do afterwards
- Add 8 + 3 by starting at 8 and counting on 3 (9, 10, 11)
- Subtract 12 − 3 by counting back 3 from 12 (11, 10, 9)
- Explain that counting on is a way to add
1 · Read
You already know how to add and take away. Counting on and counting back work for both. Instead of starting from 1 every time, you start at one number and hop forward or backward.
Leo has 12 stickers and gives away 3. He starts at 12 and counts back three hops: 11, 10, 9. Leo has 9 stickers left.
When you add, start at the bigger number. That means fewer hops to count. Say each number out loud as you hop so you do not lose your place.
Counting on adds by hopping forward, and counting back subtracts by hopping backward, from one starting number.
More to read
Add and subtract within 100: FAQ
Counting on is a way to add. For 8 + 3, start at 8. Then count 9, 10, 11. You counted 3 steps. You land on 11. Start with the bigger number to keep the count short.
3.1: Topic A- Subtraction
Counting back is a way to subtract. For 12 - 3, start at 12. Then count 11, 10, 9. You counted 3 steps back. You land on 9. Touch each number as you step back so you do not slip.
Properties of addition
Choosing a strategy matters. Counting on suits small adds. Making 10 suits numbers near 10. Splitting tens suits two digit sums. Try more than one way and pick the quick one. Explain why your pick works.
Explore more
2 · Watch
به انگلیسیTake it off screen
Where it sits
Learn first
This opens up
Nothing builds on it yet.
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.