Close counts.
Speed too.
Two numbers. Your best estimate. Ten questions.
Type your answer
or use the keypad, then hit Enter.
Accuracy and speed combine into a score out of 100. The next question arrives after a two-second pause.
Browser storage is unavailable. Personal bests will last only for this session.
?
● Purple: Least accurate or slowest.
● Green: other exact answers.
Bloops: Clear ×10, ÷10 or ÷100 mishaps can be corrected with a Bloop button below. Timing stays the same.
| Question | Guess | Correct | Accuracy | Time | Score | Bloop |
|---|
How the scores work
Every round has ten questions. Multiplication has two one-digit × four-digit, two two-digit × three-digit, three two-digit × two-digit, two one-digit × up-to-three-digit questions and one square (11²–99²), shuffled. No operand appears in more than two questions. Products stay at or below 9,999, excluding 10, 100 and 1,000 as operands. Division reverses the same balanced factor pairs and always has an integer answer.
Addition has one of each operand-length combination except one-digit + one-digit, replaced by another two-digit + two-digit. Addends are at least 6; sums stay at or below 9,999. Subtraction uses its own balanced mix: the number subtracted and the answer both have at least two digits, and the starting number stays at or below 9,999. Each round has one question from each of nine larger digit-length categories and one from a combined pool of the four smallest categories. Questions are selected uniformly within their pool and shuffled.
Actual accuracy = 100 × min(estimate, answer) / max(estimate, answer). Only exact answers display 100.0%. Timed accuracy points = max(0, 2 × actual accuracy − 100): 50% or less earns 0 points, 90% earns 80, and 100% earns 100. The table and graph keep showing actual accuracy.
The time factor is 100% through two seconds, then falls linearly towards 80% just before your 10-, 20- or 30-second deadline. At the deadline it drops immediately to 0%; you may still answer. Individual score = accuracy points × time factor. Overall score = average accuracy points × average time factor, using unrounded values. There is no root adjustment. In v1 an exact answer at six seconds earns 90 points, the same as 95% actual accuracy at two seconds. The timer turns bold amber at 80% of the deadline, and red at the deadline.
Practice has no cutoff or speed penalty: scores and PBs use average accuracy only. Total time is shown and saved, excluding feedback pauses. Practice PB summaries show the time taken in the best-scoring round. Each operation/time combination has a separate PB saved in this browser across app updates. PB messages start after the second completed round in that mode. Bloops count towards PBs; Undo restores the previous score. Optional ×10, ÷10 or ÷100 corrections require at least 80% corrected accuracy and a 40-point improvement. Timing stays the same.