Where's the Fifty?
Three envelopes lie on the table in front of you. In one of them is a fifty dollar bill. Each envelope has two statements written on it. One has two true statements; one has two false statements; and one has a true and a false statement. If you can logically determine which has the money, it is yours.
Envelope 1:
a) the money is not in here
b) the money is in envelope 2
Envelope 2:
a) the money is not in envelope 1
b) the money is in envlope 3
Envelope 3:
a) the money is not in here
b) the money is in envelope 1
Which envlope will make you $50 richer?
Envelope 1:
a) the money is not in here
b) the money is in envelope 2
Envelope 2:
a) the money is not in envelope 1
b) the money is in envlope 3
Envelope 3:
a) the money is not in here
b) the money is in envelope 1
Which envlope will make you $50 richer?
posted by Zaux at
9:41 PM
8 Comments:
the money is in envelope 3
Zaux...i use paypal
envelope 1 can be t/t,f/f,f/t or t/f.
if t/t:then the money is in #3,but that makes #2 t/t as well,so that doesn't work(#1 is not t/t)
if f/f:then the money is in #1,but that makes #2 f/f as well,so that doesn't work(#1 is not f/f)
#1 must be t/f cuz f/t doesn't work
I believe the $50 is in envelope 2
regards, Curtis
sorry, i cocked that up
regards, Curtis
Dead Simple analysis
Assume it's in #1
1a=F 1b=F
2a=F 2b=F
Two FF envelopes #1 is invalid.
Assume it's in #2
1a=T 1b=T
2a=T 2b=F
3a=T 3b=F
Two TF envelopes #2 is invalid.
Must be #3, but check statement anyhow.
1a=T 1b=F
2a=T 2b=T
3a=F 3b=F
1 TT, 1 TF, 1 FF. Valid. $$ in #3
Answer #3 has the $$
Cam
Knightmare ...'
the money has been transferred to your Paypal account :)
as usual ...Nice analysis Cam
the money is in # 3
envelope 1 has 1 true 1 false
envelope 2 has 2 true
envelope 3 has 2 false
the money is in #3 because if envelope 1 can't be the false statements, and envelope 2 can't be the false statements. Envelope 3 has to have the false statements one of which says the money is not in here.
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