Probability of at least one success
Does a 1% chance repeated 100 times guarantee a win? Predict the probability before revealing the calculation.
Predict, then reveal →Your intuition. A surprising number.
Predict first. Change the conditions. Discover why numbers can fool us — without a stopwatch or a maths degree.
A daily game and hands-on experiments for curious people. Compare your prediction with a theoretical result, then explore the explanation. No account or download required.
Experiments
Birthday paradox calculator and simulator
How many people does it take for a shared birthday to become more likely than not? Try 23 — then change the group size.
Predict, then reveal →Successive percentage discounts
20% off, then another 10% off: is that 30% in total? Predict the effective discount and compare the same starting price.
Predict, then reveal →An independent number sense lab
Gyesanwang (계산왕, “calculation king”) is made in Korea for curious people everywhere. We turn familiar mistakes about probability and percentages into predictions, experiments and short explanations.
Our simulations are educational models. We separate theory from a random run, explain assumptions and avoid invented population rankings. The games are not intelligence tests.
Start with an untimed experiment or a daily 45-second game. If a result seems wrong, send the page, inputs and expected result to [email protected].
This is a learning exercise, not a validated assessment.
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