The Last Card Problem
Three short lessons for the grown-up beside a collector: why the first cards come fast, how long a whole set takes on average, and why the last few cost the most. Then roll a die until every face has turned up.
For grown-ups, from what DeckPals teaches children at Spark & Anvil.
Roll until every face appears
You'll need: One die each, a pencil and a strip of paper with 1 to 6 written along it.
- Before rolling, everyone guesses how many rolls it will take to see all six faces.
- Roll and tick each face the first time it turns up; count every roll, repeats too.
- Write down the count when the last face appears, then play twice more.
- Add up everyone’s counts, divide by the number of games, and compare that average with about 14.7, the long-run average.