perplexus.info :: Probability : Simple coins

Simple coins (Posted on 2002-04-09)

I toss two coins and look at the outcome. I then tell you that at least one of the coins is showing up as "tails". What is the chance that the other one is showing "tails" as well?

(from techInterview.org)

See The Solution Submitted by art

Rating: 3.8750 (16 votes)

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Answer

| Comment 44 of 45 |

There are 3 possibilities with at least one tail (HT, TH, TT). Only one has both tails. Therefore, the probability is 1/3.

Posted by Math Man on 2013-01-05 13:54:19

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