Fluent addition and subtraction
Recall and use addition and subtraction facts to 20 fluently, and derive and use related facts up to 100
What a learner can do afterwards
- Rapidly recall 7 + 8 = 15 and 15 − 8 = 7
- Use 6 + 4 = 10 to derive 60 + 40 = 100
- Derive 35 + 5 = 40 from knowledge that 5 + 5 = 10
The lesson
You already know addition and subtraction facts up to 20. Now it is time to make them fast, like snapping your fingers. No stopping to count on fingers, just remember them.
Mia knows 6 + 4 = 10. She uses that fact to solve 60 + 40. She thinks: 6 tens plus 4 tens make 10 tens, which is 100.
A subtraction fact hides inside every addition fact. If you know 9 + 7 = 16, you already know 16 minus 7 = 9. Same fact, just flipped around.
Learn your facts to 20 by heart, then use the same facts to jump to bigger numbers in tens.
Watch it
Where it sits
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.
8 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.