What This Drill Trains
Mental subtraction trains the opposite habit of addition: taking away, counting back, and using complements to ten. Fluent single-digit subtraction shows up constantly in change-making, scorekeeping, and later when you borrow across tens. This drill keeps problems small so you can focus on strategy instead of large numbers.
How to Think During the Round
When the subtrahend is small, counting back is fine. When both numbers are larger, try “subtract to ten, then finish.” For 13 − 6: 13 − 3 = 10, then 10 − 3 = 7. Another strong habit is thinking of the related addition fact: “what plus 6 makes 13?” That addition recall often feels faster than counting down.
You have 60 seconds. Accuracy still outranks raw speed: one calm method repeated well beats a streak of guesses. After the timer ends, notice which problems felt sticky — that short review is where real improvement happens.
Worked Examples
Study these before you press Start. Try to recreate the thinking without looking at the answer first.
14 − 6
Thinking: 14 − 4 = 10, then 10 − 2 = 8. Or ask: 6 + ? = 14 → 8.
Answer: 8
11 − 7
Thinking: 11 − 1 = 10, then 10 − 6 = 4. Related fact: 7 + 4 = 11.
Answer: 4
9 − 5
Thinking: Direct: half of 10 is 5, so 9 − 5 = 4. Or count back five from 9.
Answer: 4
Common Mistakes
- Confusing the order and answering as if the problem were addition.
- Counting back past zero or losing track of how many steps you already took.
- Forgetting that “subtract to ten” needs a second step after you reach 10.
Practice Tips
- Say the related addition fact quietly in your head before typing.
- If you miss several in a row, pause the next round and practice only facts crossing 10.
- Keep accuracy above speed until wrong answers become rare.
Suggested Session Plan
- Read the method section once if this skill is new.
- Cover the answers and re-solve the three worked examples aloud.
- Start the timed round and stick to one strategy.
- Replay once, then write down any fact or pattern you missed.
- If the same error repeats, open the full lesson for more examples and a practice set with an answer key.
Full explanation, extra worked examples, and practice problems for this skill: open the related stage lesson .
Prefer a structured curriculum instead of random drills? Browse all learning stages or read the complete mental arithmetic guide . More timed drills live on the games hub.