Subtraction Within 20
20 questions · 60 seconds · subtraction within 20
Free · no login · instant feedback on every answer
Get fast at subtraction within 20 — the partner skill to addition facts and the second pillar of early fact fluency. The game asks 20 subtraction questions with numbers up to 20, always with whole-number answers, and shows instantly whether each answer is right.
Subtraction fluency lags addition for most students because it gets less practice, not because it is harder. A focused 60-second drill each day — especially one that corrects mistakes immediately — closes that gap quickly.
Tips That Make It Stick
- Think addition. For 15 − 8, ask "8 plus what makes 15?" Fact families mean every addition fact a student knows is a subtraction fact too.
- Subtract through ten. For 13 − 5: take 3 to reach 10, then 2 more to reach 8. Breaking at ten mirrors the make-ten addition strategy.
- Count back only for small gaps. Counting back works for 12 − 3 but falls apart for 17 − 9 — that is when think-addition should take over.
Frequently Asked Questions
What does subtraction within 20 mean?
Subtraction problems where every number involved is 20 or less, like 16 − 9 or 12 − 5. It is the standard 1st and 2nd grade fluency goal that prepares students for multi-digit subtraction with regrouping.
Why is subtraction harder than addition for kids?
Mostly practice imbalance — children encounter addition earlier and more often. Teaching fact families ("8 + 7 = 15, so 15 − 7 = 8") lets subtraction ride on addition fluency instead of being memorized separately.
Can I turn off the timer?
Yes — after loading the practice game, open game settings and switch off the time limit for untimed practice. All other preset options can be adjusted there too.
Matching Printable Worksheets
Prefer paper practice? These free PDF worksheets cover the same skill — each includes an answer key: