Daily challenge
One real case a day
A real job, a question with one right answer, and the full working. The answer is worked out when the page opens by the same engine the calculator runs, never typed in by hand; after you answer, the calculator opens with the case in it so you can check every figure. A new case each day, the same for everybody on the same date.
Practice: this is not today's case, so it does not count for your streak.
Loading today's case…
Where the answers come from
Each case is a set of inputs a real job could have: a pane and its wind pressure, a cut list and its sheets, a tube and its length. The right answer, the wrong options and every line of the working are calculated on this page by the calculator's own code: the wind-load check of the glass thickness calculator, the packer of the panel cutting optimizer, the rules of the survey sheet, the arithmetic of the budget maker, and so on. If a calculator changes, its cases change with it, and a test stops the case until a person has read it again.
When a cutting answer says "the minimum"
A cutting optimizer is a heuristic: it finds a very good layout, not always a proven best one. The cutting cases here are only ones where the optimizer's answer equals a lower bound that no layout can beat, so the right answer is the minimum, not just a good try.
Your streak, and the percentage
Your streak counts the days in a row you answer the day's case right. It is kept in this browser only. When you answer, the page sends the day, the case and whether the answer was right, and nothing else: no name, no address, no identifier. From those totals it shows what share of answers to the case were right, once there are enough of them.
These are pre-dimensioning aids
The cases teach the method; they do not sign anything. A real pane, a real cut or a real budget is checked against the project's own code and data before anything is ordered.