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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?

  Submitted by Ady TZIDON    
Rating: 3.5000 (2 votes)
Solution: (Hide)
It’s 1 in 5.
Six possible pairings can be drawn from the hat:

red 1 / red 2
red 1 / white
red 2 / white
red 1 / blue
red 2 / blue
white / blue

We know that the last has not been drawn. That leaves 5 possible combinations, so the possibility of red 1 & red 2 is 1 to 5.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
No SubjectAdy TZIDON2017-08-03 11:32:14
SolutionThe real solutionMath Man2017-05-24 09:30:46
re(2): There is only one correct answer !....SPOILERAdy TZIDON2017-05-22 17:26:35
re: There is only one correct answer !....SPOILERBrian Smith2017-05-22 12:05:40
re: There is only one correct answer ! (Baye)hoodat2017-05-22 10:54:54
Hints/Tipsre(3): Who's rightAdy TZIDON2017-05-22 03:06:48
Hints/TipsThere is only one correct answer !....SPOILERAdy TZIDON2017-05-22 03:02:19
re(5): Who's rightBrian Smith2017-05-21 23:17:59
re(4): Who's rightCharlie2017-05-21 22:13:24
Hints/Tipsre(3): Who's rightBrian Smith2017-05-21 17:15:20
Solutionre(2): Who's rightCharlie2017-05-21 16:37:54
re: Who's righthoodat2017-05-20 20:59:15
Hints/Tipsre(2): Who's right?.......I AM.Ady TZIDON2017-05-20 09:38:02
Some Thoughtsre: Who's right?broll2017-05-20 02:56:51
Hints/TipsWho's right?Ady TZIDON2017-05-20 00:41:00
re(2): I agree with BrianDaniel2017-05-19 23:38:41
SolutionSolutionhoodat2017-05-19 23:10:27
re: I agree with BrianCharlie2017-05-19 23:01:06
I agree with BrianSteve Herman2017-05-19 13:28:44
SolutionSolutionBrian Smith2017-05-19 12:43:07
SolutionSolutionJer2017-05-19 11:56:13
SolutionSolution Charlie2017-05-19 11:00:34
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