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/sci/ - Science & Math

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5992689 No.5992689 [Reply] [Original]

A total of 16 pills are on a table; all of them are the same size and the same appearance, but one of them (the poisonous one) weighs more than the others. Using a balance scale, how can you be positive as to which one is the poisonous one... With only 3 weighs?

>> No.5992733

Are you fucking serious? weigh the pills against eachother. Derp.

>> No.5992736

>>5992733

Only have 3 chances to weigh them.

>> No.5992744

1: 8 and 8
2: 4 and 4
3: 2 and 2

Then you have a 50/50 chance. Eat one. If you die, then that's the one that was poisonous.

>> No.5992752

>>5992744
I wish it was that simple

>> No.5992753

>>5992744
Couldn't you just do to 8v8 and then eat one from the side that weighs the least

>> No.5992755

>>5992753
It's to determine the poisonous one, not eat a safe one

>> No.5992758

>>5992755
Why would I want to find a poisonous one? Just throw them all away after you eat your pill.

>> No.5992759

>>5992758
>how can you be positive as to which one is the poisonous one... With only 3 weighs?

>> No.5992760

>>5992759
why would you want a poisonous one?

>> No.5992761
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5992761

Weigh 6 vs 6 and leave 4 aside. If they are the same, you know it's one of the 4... then the remaining two weighings are 2v2 and 1v1.

If one of the two sixes is heavier, weigh it 3 vs 3 (taking the heaviest) and then 1v1 with 1 laid aside.

Three weighings no matter what.

>> No.5992768

Put five on each side. Balanced? No pill.

Then put two on each side. Balanced? No pill.

Then put weigh the remaining two and find the poisonous one.

Trust me, I'm a Jew.

>> No.5992764

>>5992689
Break into 2 piles of 5 and 1 pile of 6.
Weigh both 5 piles, break heavier into 2 of 2 and leave 1, weight both 2, break heavier into 1 and 1 (if equal was spare from breaking up 5)

If both 5 are equal, break 6 into 3 piles of 2, weigh 2 of the piles, still have one weight left for the heavier pile.

>> No.5992770

>>5992769
i think my last two steps weren't written clearly. there should never be more than 3 measurements needed.

>> No.5992769

divide into 4 groups 5,5,5,1
measure groups 1 and 2
If one groups is heavier split into 3 groups 2,2,1
if same weight split group 3 into 3 groups 2,2,1
measure groups 1b and 2b
if one group is heavier split into 2 groups 1,1
measure
if same weight measure groups 3b and 4

>> No.5992771

>>5992768

I'm sorry, for that last step if the two on each side are balanced then the last one is poisonous. If they tilt then weigh the two on the heavier side to see which is heavier.