perplexus.info :: Probability : Fifty-fifty?

Fifty-fifty? (Posted on 2016-02-18)

There are 3 coins in a bag. One is a normal coin with "heads" on one side and "tails" on the other. The second one has "heads" on both sides and the third has "tails" on both sides.

Randomly draw one coin from the bag and put it on the table without looking at the down face.

The up face is a “heads”.
What is the probability the down face is “tails”?

Please justify your answer.

Submitted by Ady TZIDON

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Solution: (Hide)

The answer is 1/3.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Simplistic answer	Johno Zapatek	2016-02-18 15:33:04
Solution	Brian Smith	2016-02-18 11:41:46

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