Fluent adding and subtracting within 20
Fluently add and subtract within 20 using mental strategies; know from memory all sums of two one-digit numbers
What a learner can do afterwards
- Answer any single-digit addition fact within 3 seconds
- Recall subtraction facts within 20 from memory (e.g. 15 − 8 = 7)
- Use known addition facts to derive related subtraction facts rapidly
The lesson
You already know how to add and subtract within 20. Now it is time to get fast. Fluent means you know the answer right away, in about 3 seconds, without counting on your fingers.
Mia sees 7 + 8. She already knows 7 + 7 = 14, so she just adds one more: 15. No counting needed.
Fast facts come from tricks like doubles, making a ten, and fact families, not from counting one by one. A little practice each day makes them stick.
Know it, don't count it: use doubles, make-a-ten, and fact families to answer in a snap.
Watch it
Where it sits
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.