Wikipedia:Reference desk/Archives/Mathematics/2019 December 31

= December 31 =

Last puzzle of 2019
“I am a time traveller!” said the time traveller. “Bullshit!” said I. “I will prove it to you. Get a fair dice. Color the side 1,2 and 3 as red. Color the sides 4 and 5 as green. And finally colour the side 6 as blue.” I did as the traveller asked.

“Now I will write down the color which you will roll” said the traveller and wrote down something on a piece of card which was placed face down so I could not see what was written.

“Roll the die!” the time traveller demanded. I did. “now watch this!” the traveller said and turn over the card.

The card showed a word correctly described the color of the side of the dice which I rolled.

Question: Assuming the time traveller is a Fraud, what is the probability of writing down the correct result on the card before I rolled the dice? 49.177.234.140 (talk) 08:28, 31 December 2019 (UTC)


 * –Deacon Vorbis (carbon &bull; videos) 14:12, 31 December 2019 (UTC)

Not quite Maths (and may only work in English), but how about certain? 6 — Preceding unsigned comment added by 213.31.114.2 (talk • contribs) 10:34, 1 January 2020 (UTC)


 * The answer depends on how the "time traveller" chooses the word that she writes on the card. If she makes a random choice between "red", "green" or "blue" then the probability of writing down the correct colour is 1/3. However, if she always writes "red" then the probability that she is correct is 1/2. And if she always writes "blue" then the probability that she is correct is only 1/6. Gandalf61 (talk) 14:34, 3 January 2020 (UTC)