10% trick is instant
Sliding a decimal left is a built‑in shortcut: 10% of any number is just “shift left”. From there, 5% is half of that, and 1% is one more shift.
Fast arithmetic recall across your selected skills.
Skills: addition to 100, subtraction to 100, times tables, percentages, fractions, squares
Practice short daily rounds, review mistakes immediately, and repeat weak question types until common shortcuts become automatic.
Addition, subtraction, multiplication, division, number bonds, doubles, halves, times tables, decimal bonds, fractions of amounts, percentages, and square numbers.
Yes. Easier ranges suit upper elementary practice, while harder settings support middle school, adult numeracy, and speed drills.
Yes. Turn on Daily Seed so everyone gets the same question sequence for the day.
Speed rounds rank by correct answers. Ten-question rounds save best accuracy. Live stats show accuracy, streak, and correct answers per minute.
Decimal answers allow a small rounding tolerance of ±0.01. Integer-only facts require exact whole-number answers.
Yes. During mobile rounds the play area focuses on the question, answer field, keypad, timer, and score.
Mental math improves when recall and shortcuts are practiced together. Start with one or two skills, answer quickly, then use the review table to repeat missed or slow question types. The weak-spot mode remembers broad skill areas locally, such as times tables or percent shortcuts, and brings them back more often in future rounds.
10% of 240 is 24. 5% is half of that, 12. 25% is a quarter, so 25% of 64 is 16. 50% is half. For 1/3, divide by 3; for 2/3, double the one-third result.
Double 48 by doubling 50 then subtracting 4: 96. Half 86 by splitting 80 and 6: 40 + 3 = 43. Number bonds ask what completes 10, 20, 50, 100, or 1.00.
Use anchors. 19² is (20 - 1)² = 400 - 40 + 1 = 361. 31² is (30 + 1)² = 900 + 60 + 1 = 961.
Break hard facts into friendly parts. 7 x 12 is 7 x 10 plus 7 x 2, so 70 + 14 = 84. Division facts use the same relationship in reverse.
Getting started is easy. Follow these steps to set up a session that matches your goals:
This trainer works well for upper elementary, middle school, homeschool, tutoring, adult numeracy, and quick classroom warm-ups. Use Daily Seed when a class needs the same questions, or set one skill such as multiplication 2-12 for a focused bell-ringer. No account is needed, and practice data stays in the browser.
A simple 5-minute routine: 60 seconds of warm-up, 2 minutes on one weak skill, 60 seconds of mixed speed practice, then 1 minute reviewing mistakes and retrying them.
Release note: the trainer now includes broader arithmetic skills, per-question cutoff options, weak-spot practice, and persistent mistake review.
Sliding a decimal left is a built‑in shortcut: 10% of any number is just “shift left”. From there, 5% is half of that, and 1% is one more shift.
Competitive “mental” mathletes often visualise an imaginary abacus (soroban). World champions add or multiply 15+ numbers in under 10 seconds using that mental image.
Consecutive squares differ by odd numbers: n² − (n−1)² = 2n−1. Memorising a few anchors lets you jump to nearby squares faster.
For fractions of a whole, a quick cross-multiply check (a×n vs. b×answer) flags slips immediately—handy under a timer when digits blur.
Humans add fastest in chunks: 17% of 240? Take 10% (24), 5% (12), 2% (4.8) → 40.8. Decomposing beats long multiplication every time.