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Skill Gym · Cognitive

Mental Mathematics

Compute fast and accurately without paper, then sanity-check the answer.

Rep 1 of 8 · difficulty 2/60 correct
Number Sprint

Adaptive rule: two correct in a row raises difficulty, one miss lowers it. Accuracy so far 0%.

Mastery
0
Score
0% of target 88
Reps logged0
Accuracy0%
Difficulty2 / 6
Method
Interleaved retrieval
from Robert Bjork's desirable-difficulty research

Mixed problem types beat blocked repetition for long-term recall.

Game task
Number Sprint

Beat the clock as difficulty tracks your accuracy.

See this skill on your development profile
Arcade · 60-second games

Play to train mental mathematics

🏆 0Number Sprint⏱ 60s
Mental maths speed · 60 seconds
Number Sprint

A sum appears with a shrinking time bar. Answer before it runs out. Harder sums and less time as you stay accurate.

Your best: 0

Beginner level

Start here: learn it, check it, use it

Beginner lesson

Break numbers into friendly parts, work left to right, and estimate first so you notice wrong answers.

  1. Estimate: round each number and guess the answer.
  2. Split: 47 + 38 = 40 + 30, then 7 + 8.
  3. Combine the parts.
  4. Compare with your estimate.
Worked example: 26 × 4 → (20 × 4) + (6 × 4) = 80 + 24 = 104. Estimate 25 × 4 = 100 — close, so 104 is believable.
Beginner check · 0/3
58 + 27 = ?
Best estimate for 49 × 3?
15 × 6 using splitting:
Real-life task

At the next shop visit, add up three prices in your head before the bill appears. Check against the receipt.

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