The riddles and trivia thread

[Threeme2189]

Anyone?
Do you need a hint?

[GraysonK]

Weigh half of them, then weigh the other half and subtract the difference. 

[Threeme2189]

Weigh half of them, then weigh the other half and subtract the difference. 

You don't know if the counterfeit coin is heaver or lighter than the rest, only that its weight is different.

[jan.]

Weight 2 groups of 3 coins and one group of 4 coins.
Than you can know the weight of one coin.

[AimlessWanderer]

if we number coins one to ten ...

(I am assuming these are balance scales not digi)

First Weigh
1, 2, 3, 4 against 5, 6, 7, 8    (9 & 10 off the scales)
If the scales tip then 9 and 10 are sound and one of the other 8 is duff
If the scales balance then 9 or 10 is duff

Second Weigh
If it's 9 or 10 thats the oddbod - just weigh one of them against any one of the 8 that's sound and you'll know which is which. If scale tips its the one on there if not it's the other

if it's one of the 8 thats dodgy - swap two from each side and remove another
1,5,6, against 7,2,3, (4 and 8 removed)
If it stops the same then it's either 1 or 7 is duff (one more weigh like with 9 or 10 will determine it)
If it balances then it's 4 or 8 that's the imposter (again one more weigh will fix it)

If the scales change direction then it's either 5,6,2 or 3 which is duff. which basically means you've run out of ways to determine the fake. As this can't then be solved in one more weigh, take all 10 coins to the pub and spend them on beer. You will feel much better and now it's someone elses problem

 

[AimlessWanderer]

I must add that was my first run through, and after that I did stumble upon a solution that worked (I think). I decided to go with my original for the post though and let someone else pick up the credit as I have no riddles to offer in return - besides I preferred my first answer 

[Threeme2189]

Jan, your answer is incorrect, and I don't really understand it
Can you explain further?

50ft-trad, your original answer is pretty close, but like you say it isn't correct.
As you can see, there are several possibilities and outcomes to explain in the solution.
I'll give this one a couple more days, and if nobody solves it then I'll give you a (very helpful) hint.

By the way, I want to clarify that it is a balance scale and not a digi scale.

Good luck!

[Threeme2189]

Ok, here's a hint:

The 1st time you weigh the coins it's 3 and 3.

[AimlessWanderer]

  It's gone quiet....
Here's what I ended up with after my "spend them on beer" conclusion ...

Weigh one
1,2,3 vs 4,5,6 If it tips, the duff coin is one of these 6, if it balances it's one of the remaining 4

Weigh two
If weigh one tips - weigh 1&4 against 2&5. Tipping the same way means it's 1 or 5, tipping the other means its 2 or 4 (as they swapped sides) and balancing means it's 3 or 6. If weigh one balances - weigh 7 & 8 against 1 and 2. If it tips it's either 7/8 or 9/10. 

Weigh three
By now you've narrowed it down to two coins, and weighing either one of the pair against any on the known norms will lead you to the culprit.

Sorry, I've no riddles to offer in return  and I still preferred my first answer 

[tattoosteve99]

Ok here's another one. If a tree falls in the forest and nothing is around to here it does it make a sound?

[Pacu]

Ok here's another one. If a tree falls in the forest and nothing is around to here it does it make a sound?

technically no but the deaf person it hits does.

[tattoosteve99]

Wow Most people says it does make it a sound. Actually it doesnt. Sound is by definition something someone or something can hear. Great job there.

[Nikos]

Wow Most people says it does make it a sound. Actually it doesnt. Sound is by definition something someone or something can hear. Great job there.

Exactly! "Can hear"... not "has heard". It does make a sound (air waves, pulsing in acoustic frequencies, propagating spherically, etc.) no matter whether someone is there to hear it or not.