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Four balls (Posted on 2017-05-19) Difficulty: 2 of 5
There are four balls in a hat: a blue one, a white one, and two red ones. Now I draw simultaneously two balls, look at them, and announce that at least one of them is red.

What is the chance that the other is red as well?

See The Solution Submitted by Ady TZIDON    
Rating: 3.5000 (2 votes)

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No Subject Comment 22 of 22 |

Out of the set  (R1, R2, W, B) there are 6 possible draws of 1 pair: 

(R1W,. R2W, R1B, R2B, R1R2, BW) .

The first  five justify announcing: "at least one is red" , but only one out of those five consists of two red balls.

So the answer is 1/5 i.e, 20%.

Edited on August 4, 2017, 1:40 am
  Posted by Ady TZIDON on 2017-08-03 11:32:14

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