6 questions, answered one at a time. You find out straight away whether each answer is right, and why. Nothing is sent anywhere and no score is recorded except in this browser, where you can clear it whenever you like.
How the questions are made
The arithmetic questions are generated, so the numbers differ from the examples on the method pages and the correct answer is worked out rather than typed. The wrong options are not random either. Each one is the number you get by making a specific mistake: dropping a minus sign, subtracting digits instead of place values, or leaving out one of the partial products. Picking a wrong option therefore tells you which mistake you made, and the explanation says so.