Much much tougher brain teaser

PorscheNGuns · #1 08-09-2005, 03:10 AM

Most OOTers are probably not smart enough to figure this one out on their own, but nonetheless, don't spoil it if you know it.

You have 12 rocks and a scale, and 11 of the rocks weigh exactly the same. The remaining rock is either heavier or lighter than the other 11.

Using the scale only 3 times, figure out which one of the rocks is the odd one out, and whether it is heavier or lighter.

You only get one chance, I am holding a .357 mag to your head, and if you screw up, I blow your brains out. Go!

-Matt

cnfuzzd · #2 08-09-2005, 03:12 AM

pick up scale. Bash you in head 3 times. Problem solved.

peace

john nickle

Luzion · #3 08-09-2005, 03:20 AM

is that even possible? not knowing if that 12th special rock is heavier or lighter really makes it impossible

ClaytonN · #4 08-09-2005, 03:29 AM

soab. i can definitely figure it in 4, but not 3. hold on.

Stuey · #5 08-09-2005, 03:46 AM

so it's like a puzzle with socks. if you think about it.

deadmoney98 · #6 08-09-2005, 04:00 AM

Separate the rocks into 3 equal piles of 4. Weigh each, the odd one out contains the different rock (rock X). This also will tell you if it is lighter or heavier and the weight of each individual other rock (Y).

Take two rocks from the group you now know contains rock X and weigh them. If they weigh 2Y, take one of the two remaining rocks and weigh it. It is either X or a Y.

If they don't weigh 2Y, pick one and weigh. It is either X or a Y.

Obviously if the rock weighs Y, the other rock is X and vice versa.

Matty · #7 08-09-2005, 04:01 AM

that's more than 3. that's like 5.

Josh W · #8 08-09-2005, 04:03 AM

Is it a scale like "this weighs 10 lbs."? Or a balance like "this side weighs more than that side"?

Josh

Stuey · #9 08-09-2005, 04:04 AM

you can only use the scale 3 times.

So if you weigh the first 2 piles of 4 rocks and they are not equal your methods fails. If you get lucky and they are equal it works though. Good chance I'm blowing smoke here. [img]/images/graemlins/blush.gif[/img]

Luzion · #10 08-09-2005, 04:07 AM

[ QUOTE ]
Separate the rocks into 3 equal piles of 4. Weigh each, the odd one out contains the different rock (rock X). This also will tell you if it is lighter or heavier and the weight of each individual other rock (Y).

Take two rocks from the group you now know contains rock X and weigh them. If they weigh 2Y, take one of the two remaining rocks and weigh it. It is either X or a Y.

If they don't weigh 2Y, pick one and weigh. It is either X or a Y.

Obviously if the rock weighs Y, the other rock is X and vice versa.

[/ QUOTE ]

Wait wait wait... I want to clarify something.... What kind of scale are we using? Are we using something that weighs the thing you put in it? Or are we talking about a scale like this...