Short arithmetic sets with an explanation behind every answer and a per-skill breakdown at the end. A mixed workout draws from addition, subtraction, multiplication, division, squares, and percentages, then reports each one separately with the time it took — so you finish knowing which arithmetic is actually slow, not just that ten questions happened.
Step by step
01Pick the arithmetic
Mixed rotates through all six skills — addition, subtraction, multiplication, division, squares, and percentages — and is the one that diagnoses. A focused set is what you run afterwards, once you know which skill needs the repetitions.
02Set the length and the level
Sets run from five to twenty questions. The level widens every number range at once: at level 1 sums stay under 25 and percentages are 10, 25, or 50; by level 10 sums reach 150, products reach 12×18, and the percentage set includes 5, 15, and 75.
03Answer, then read the explanation
Type the number and press Enter. Right or wrong, you get a short route to the exact answer — decompose into friendly parts, find 10% and halve it, count up rather than back. That is the part worth reading when you were right by luck.
04Use the breakdown, not the score
The panel under the question tracks accuracy and average seconds for each skill as you go. Nine out of ten with every miss in percentages is a different session from nine out of ten spread evenly, and it tells you what to do next.
Why this one
Per-skill accuracy and pace
Every answer is filed under the skill it tested along with how long it took. A mixed set therefore ends with a reading per skill instead of one average that hides the weak one.
Explanations, not just corrections
Each question carries a method: split the second number into tens and ones, count up from the smaller value, take 10% and add half of it. Knowing the answer teaches nothing; knowing the route transfers to the next question.
A difficulty you control
Most drills either stay easy forever or ramp on a schedule you did not choose. The level here is a slider, so you can sit at the edge of comfortable — which is where practice actually does something — instead of grinding through numbers you already know.
Sets are reproducible
Questions are generated from a seed carried in the URL. Share the link and someone else gets the same twenty questions, which makes two scores comparable; hit 'same questions again' and you can measure a second attempt honestly.
Exact percentage answers
The percentage generator picks the base value from the percentage — twentieths for 5% and 15%, quarters for 25% and 75% — so every answer is a whole number. You are never marked wrong for rounding a question that should not have had a fraction.
No countdown by default
Pace is measured and reported, but nothing expires. Timed pressure trains a different thing than retrieval, and it makes people guess; the average-seconds column gives you the speed signal without the panic.
FAQ
Practise retrieval in short sets rather than long sessions, and always look at the method after answering. The gains come from recognising friendly decompositions — 47 + 28 as 47 + 30 − 2, 15% as 10% plus half of 10% — until they stop needing conscious thought. Ten minutes a day beats an hour on Sunday.
Find 10% by moving the decimal one place, then build from it. 20% is double that, 5% is half, and 15% is 10% plus 5%. For 15% of 80: 10% is 8, 5% is 4, so the answer is 12. For 25% and 75%, quartering is faster than the decimal route.
Not while you are still learning the methods. Speed under pressure encourages guessing, and a guess that happens to be right teaches nothing. This gym records your average seconds per question so you can watch pace improve, but nothing runs out — accuracy first, and speed arrives as a side effect.
Start at 5 and move once you are consistently above 80%. If you are missing questions because the numbers are large rather than because the method is unclear, drop a level or two: practice at the edge of your ability is useful, practice past it is just frustrating.
Yes — pick add, subtract, multiply, divide, or percent instead of mixed. (Squares come up inside the multiply and mixed sets.) The usual pattern is to run a mixed set to find the weak skill, drill that skill on its own for a few sets, then return to mixed to check whether the gap actually closed.
In this browser's localStorage, as lifetime totals and a short list of recent sets. Nothing is uploaded, there is no account, and the share link carries only the mode, length, level, and question seed — never your answers.
Every question is generated and graded in your browser. Answers are never transmitted, progress stays in localStorage on this device, and the share link carries only the workout settings and seed.
Keep going
Typing test
Measure WPM and accuracy, and find the keys costing you time.
Code reading gym
Predict JavaScript output, then trace what actually ran.
Percentage calculator
Every percentage question, with the working shown.
Average & median
Mean, median, mode, and spread for a list of numbers.