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The Magic Cafe Forum Index » » Puzzle me this... » » An old coin problem - new questions??? (0 Likes) Printer Friendly Version

Nir Dahan
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I read in one of Martin Gardner's books (who else) the following puzzle.

q1 (easy): you have 6 sacks with 100 coins each is exactly 1 gram. one sack contains all counterfeit coins which are 1 milligram heavier than usual.
with an electronic scale (accurate to 1 milligram) identify with a single weighting the sack containing the counterfeit coins.

this one is old an deasy and the forum member know it for sure

q2 (a bit less easy): again 6 sacks, again 100 coins each. now the counterfeit coins can be in more than one sack, they can even be in all or none!
again using one weighting with the electronic scale - identify the counterfeit sacks.

this is a slight elaboration of the previous question but still fairly well known.

q3 (harder): 6 sacks, 24 coins in each this time. none, one, some or all the sacks might contain counterfeit coins. again as before, use the scale one time to identify the problematic sacks.

this version I first read in the Gardner book - and I found it great, you will appreciate it when you solve q2 and see that your solution doesn't work here...

q4 (hard - I dare say): given 6 sacks what is the minimum number of coins needed per sack to identify (using the scale only once) if one sack, some sacks all sacks or none contain counterfeit coins.

q5 (even more hard - I think): what about n sacks with n coins - can you find a rule.

---
q4 and q5 are my own (to my knowledge) extensions - if not please feel free to correct me. I do not have definitive solutions to them and would love to get some help.

ND.
Scott Cram
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Q5 - the answer is yes, you can find a rule.
;)
Nir Dahan
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And what is it?
Scott Cram
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Let us work on the first 5 questions before you add new questions! Smile
Mr. Ray
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LOL
The Magic Cafe Forum Index » » Puzzle me this... » » An old coin problem - new questions??? (0 Likes)
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