Mental Math Cheat Sheet & Trainer

A compact, practice-ready set of mental math shortcuts, examples, and mnemonics. Designed for fast recall and 5-second drills.

• Main sheet: see mental_math.md
• Interactive trainer: see mental_math_trainer.html
• Audience: students, interview prep, speed arithmetic fans, and anyone who wants faster everyday math.

What's inside

Cheat Sheet (mental_math.md)

• Addition & subtraction shortcuts (round-and-fix, complements)
• Multiplication patterns (×9/11/25/75/125, near-base tricks, cross-add)
• Division, percentages & conversions (÷5/9/12, quick % chunks, °F/°C)
• Squares & cubes (ending-in-5 squares, difference of squares, near-100², quick cubes)
• Roots & estimates (linear approximations for √ and ∛, near-10000 √)
• Bonus mini-tricks and a step-by-step practice plan

Interactive Trainer (mental_math_trainer.html)

• Timed mental math practice sessions
• Customizable difficulty settings (operand ranges, time limits)
• Support for addition, subtraction, multiplication, and division
• Built-in hints based on mental math techniques
• Integrated cheat sheet with quick reference tips
• Performance tracking and statistics
• Fixed operand practice (e.g., focus on specific times tables)

Open mental_math.md for the full, formatted tables and examples, or mental_math_trainer.html in your browser for interactive practice.

Quick start

Using the Cheat Sheet

1. Open mental_math.md and pick ONE shortcut.
2. Create a mini-set (8–10 problems) matching that rule.
3. Solve only with that shortcut; aim for ≤5s per problem after warm-up.
4. Check answers quickly. Add a second shortcut once comfortable.

Tip: Use a timer (phone/desktop) and track your average time per set.

Using the Interactive Trainer

1. Open mental_math_trainer.html in your web browser.
2. Configure your practice settings (operators, number ranges, time limit).
3. Click "Start Game" to begin a timed practice session.
4. Use the built-in "Hint" button to see mental math techniques for difficult problems.
5. Access the "Cheat Sheet" button for quick reference to mental math tricks.
6. Review your performance statistics after each session.

Tip: Start with smaller number ranges and work your way up as you improve.

Printing / formatting

• The sheet is optimized for plain-text editors where tables still align.
• For print: export to PDF from your editor/markdown viewer. Use a monospace font for best table alignment.
• If your viewer collapses pipes (|), try enabling code/monospace rendering or export to PDF.

Contributing

Contributions welcome! Ideas that help:

• Clearer examples or mnemonics
• Additional quick methods with rationale
• Small correctness fixes or formatting improvements

Workflow:

• Edit mental_math.md (keep tone, keep tables compact)
• Keep examples correct and mentally computable without a calculator
• Avoid inline HTML (e.g., <br>) inside tables; use separators instead (e.g., •)

License

Add your preferred open-source license (e.g., MIT) here.