▶ Playable Free
🎯
⚡
🧠
📊
🧩
Logic & Puzzles
Monty Hall — Three Doors
Behind one of three doors is a car; the other two hide goats. You pick door 1. The host opens door 3 to reveal a goat. Should you switch to door 2? What's the probability of winning if you switch (as a percent)?
Logic Puzzle — No Sign-up
🧩 Logic puzzle
✓ 0
4.7★
Brain Score
Medium
Difficulty
60s
Round
📝 What it trains
Monty Hall — Three Doors — A classic logic puzzle that exercises deductive reasoning, attention to detail and step-by-step planning. Read the problem carefully, work it out, then enter your answer. The solution and full explanation are revealed when you submit.
- Processing speed — how fast your brain handles numerical information.
- Working memory — holding partial results while you compute.
- Sustained attention — staying accurate as the timer pressures you.
🎯 How to play
- Press Start Drill — a new problem appears every round.
- Solve in your head — no scratch paper.
- Type the answer and press Enter.
- Correct answers extend your streak; wrong answers cost no time but reset the streak.
- You have 60 seconds. Beat your high score, then share your result.
🧪 The science
Mental arithmetic recruits the parietal cortex (number magnitude), prefrontal cortex (working memory) and the basal ganglia (procedural fluency). Daily 5-minute drills have been shown to improve fluid intelligence scores in adults over 8 weeks.
Bergman-Nutley & Klingberg (2014). Effect of working-memory training on working memory, arithmetic and following instructions. Psychological Research 78(6), 869-877.
💡 Tips & strategy
- Chunk large numbers — 47 + 38 = (40 + 30) + (7 + 8) = 85.
- Round and adjust — 98 × 4 ≈ 100 × 4 − 2 × 4 = 392.
- Memorize squares to 25² — speeds up multiplication and percentages.
- Aim for accuracy first — speed comes naturally with practice.
❓ Frequently asked
Is it really free?
Yes — every exercise on Brain Training is free. No sign-up, no paywall.
How long should I train each day?
Research suggests 5–15 minutes daily produces measurable gains in 4–8 weeks. Consistency beats long sessions.
Does mental math really make you smarter?
It improves processing speed and working memory directly, with modest transfer to fluid reasoning tasks.
Is there a mobile app?
Yes — "Brain Training: Math & Memory" is free on iOS App Store and Google Play.
