🏋️ The mental math gym

Train your mental math & logic

Timed brain workouts. Build combos, earn points, and get faster one round at a time.

🧮 Mental Math

Break numbers into tens and ones, add the big parts first, then adjust. Regular timed reps build automatic recall.

Use the distributive trick: 23 × 7 = 20×7 + 3×7. Round to a friendly number, multiply, then correct the difference.

10% is just moving the decimal one place. Build any percent from 10%, 5% and 1% chunks.

Average = total ÷ count. To compare means, work from a base value and average the differences.

Round the divisor to a clean number, divide, then nudge the result. Keep only the significant digits you need.

Keep the first 2–3 significant digits of numerator and denominator, then divide. Cut more or fewer digits based on how close the options are.

To compare a/b and c/d, form the "difference fraction" from the gaps and compare it with the smaller fraction.

Growth rate = (current − base) / base × 100%. Use truncated division to pick the answer without computing every digit.

Share = part / total × 100%. To judge a change in share, compare the growth of the part with the growth of the total.

Multiple = A / B. When the gap is large, truncate to the first two significant digits — that is usually precise enough.

Check the differences between terms first. Constant difference → arithmetic; constant ratio → geometric.