BrainDen.com - Brain Teasers
• 0 ## Question If you choose an answer at random, what is the chance you will get it correct?

a) 25%

b) 50%

c) 60%

d) 25%

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• 0 If I understand right, there are 12 possible scenarios

A1 = 25% (you choose a,b,c,d)

A 2= 50% '' ' ' ' ' '

A 3= 60%' ' ' ' ' ' ' '

A1 = 2/4 correct random

A2 = 1/4 correct random

A3 = 1/4 correct random

so you have a 1/3 chance of guessing correctly at random

right?

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• 0 Thinking transversely

Any multiple choice question with 4 answers normally gives you a 25% chance of a random guess being right but in this case two answers are correct an two are wrong which would lead one to 50% chance of getting the answer correct which makes it appear that 50% is the correct answer but if 50% is the correct answer then we are back to only 25% chance of a random guess being correct.

Collusion: choosing 50% and 60% would be wrong for the chance of selecting 50% at random is only 25% and 25% is wrong for if that were the solution, then the real answer is 50%.

so this is an unsolvable paradox.

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• 0 Maybe I don't understand...

Are A,B,C,D supposed to be our choices? Or are we to assume they and the 25%,50%60% are an imaginary test question where one of those 3 values is a correct answer, and we determine the prob that a random guess will be right?

If the prior, you have to determine the scenarios by value of the answer not by a,b,c or d.

You cant consider A is the answer so A and D are right AND D is the answer so D and A are right

You can only say

25% is the answer (50% to guess right)

50% is the answer (25% to guess right) or

60% is the answer (25% to guess right)

Edited by SleepingGiant

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• 0

Heh. I saw this on Casey McKinnon's G+ the other day.

A lot of people said 33%, but I completely disagree with that answer.

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• 0 Personally I agree with this answer...

Thinking transversely

Any multiple choice question with 4 answers normally gives you a 25% chance of a random guess being right but in this case two answers are correct an two are wrong which would lead one to 50% chance of getting the answer correct which makes it appear that 50% is the correct answer but if 50% is the correct answer then we are back to only 25% chance of a random guess being correct.

Collusion: choosing 50% and 60% would be wrong for the chance of selecting 50% at random is only 25% and 25% is wrong for if that were the solution, then the real answer is 50%.

so this is an unsolvable paradox.

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• 0 If we allow write-in answers, it's 0%. Since none of the above answers are correct, it's impossible to get it right with random selection, hence 0%.&nbsp;

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