top button
Flag Notify
    Connect to us
      Site Registration

Site Registration

You hold 10 cards, the Ace through 10 and you lay them randomly down in a row...

+1 vote
152 views

You hold 10 cards, the Ace through 10 and you lay them randomly down in a row.

Now you turn them over one at a time starting with the first. Each time you turn a card face up, that card tells you the position of the card to flip over next. Once it tells you to flip over a card that is already face up, you are done.

What is the probability that you will turn every card face up?

posted Nov 11, 2018 by anonymous

Share this puzzle
Facebook Share Button Twitter Share Button LinkedIn Share Button

1 Answer

0 votes

To reach the final card The first card has to be anything but 1: (9/10)
Similarly for the 2nd card (8/9)
Since all the events are to happen one after the other the probabilities are to be multiplied,
(9/10)*(8/9)*(7/8)*(6/7)*(5/6)*(4/5)*(3/4)*(2/3)*(1/2) = 1/10

answer Nov 11, 2018 by Tejas Naik



Similar Puzzles
0 votes

A standard deck of 52 playing cards is shuffled. The cards are turned up one by one until an ace appears. Is the next card—the one following the 1st ace—more likely to be the ace of spades or the two of clubs?

0 votes

You open a brand new deck of cards, and the cards are arranged in increasing order by the suits hearts, clubs, diamonds, and spades.

The 10th card, for example, is the 10 of hearts. There are 52 cards in all. You shuffle the deck thoroughly. How many cards, on average, will still be in the same spot as before the deck was shuffled?

...