BRAIN TEASERS THREAD

[DCopper04]

[ QUOTE ]
It takes 10 men 8 days to dig 13 holes. How long would it take one man to dig half a hole?

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Answer: <font color="white"> 40/13 days?</font>

[Magic_Man]

One of my favorites from long ago, I hope I get it right. I have purposefully changed the usual wording to prevent easy googling:

A &amp; B are integers greater than 1 and less than 100.

Mr. Add knows (A+B)
Mr. Multiply knows (A*B)

Mr. Add says to Mr. Multiply, "You don't know A and B."
Mr. Multiply says, "Now I do know A and B."
Mr. Add says, "Now I do too."

What are A &amp; B?

~MagicMan

[Eihli]

According to the late philosopher and logician George Boolos, who was a professor at MIT, the hardest logical puzzle is one that was invented by the logician and puzzle-master Raymond Smullyan, and modified slightly by the computer scientist John McCarthy. Here is the puzzle :

Three gods A , B , and C are called, in some order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A , B , and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer in their own language, in which the words for yes and no are “da” and “ja”, in some order. You do not know which word means which.

This was posted in OOT years back. I have held off looking up the answer.

[Winenose]

This looks interesting..

I assume that first saying means that A*B has at least two sets of A and B that can make it.

First number like this is 12. It can be found by 2x6 and 3x4. Next is 16, then 18, then 20, 24, 28, 30, etc..

And that's where my ideas run out.

[ScottHoward]

[ QUOTE ]
It takes 10 men 8 days to dig 13 holes. How long would it take one man to dig half a hole?

[/ QUOTE ]
wtf is half a hole?

[Borodog]

[ QUOTE ]
[ QUOTE ]
It takes 10 men 8 days to dig 13 holes. How long would it take one man to dig half a hole?

[/ QUOTE ]
wtf is half a hole?

[/ QUOTE ]

Hence the correct answer is an infinite amount of time, since you can never dig half a hole.

[Drunken Monkey]

[ QUOTE ]

RIDDLE #2 - DIFFICULTY RATING 8.5/10

You have 12 coins, 11 weigh the exact same amount but one (you don't know which) is of a different weight (you also don't know whether its heaver or lighter. you have a scale, using 3 weighings figure out which coin is the odd one and whether it is heavier or lighter.

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Is this a scale where you put a coin on it and it gives you a numerical weight of that coin? Or is it a scale where you compare two items by placing them in different plates and watching which way the bar is tipped (a balance scale)? I am assuming the latter, but I just wanted to be clear.

Also, where did you get this rating system?

[ScottySo]

in riddle #1 you have a bathroom scale, i.e. you put your coins on it and it gives you the weight. in the second one is a balance scale to compare weights. the guy on the first page got it right.

[valenzuela]

We have 3 cannibals and 3 explorers and a boat that has the capacity for 2 ppl. How do you pass all 6 persons safely from one side fo the river to the other of the river?
If there is ever more cannibals than explorers on either side the cannibals will eat the explorers.

[metsandfinsfan]

again guys if you post these in pog you will get more responses

although i think we have seen most of these already