weights and measures

Anything goes, but keep it seemly...

Postby coloin » Wed Jul 05, 2006 8:12 am

udosuk wrote:If you have exactly 1 different coin (heavier or lighter, we don't know) out of 12 coins, only 3 balancings are enough to pick it out.


Yes I can now how see that is possible

Hud wrote:With two of ten coins of the heavier variety, I need 5 weighings to sort out the two copper ones


Yes this can always be done in five weighings.........12 again is the upper limit of the number of coins.

C
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Postby udosuk » Wed Jul 05, 2006 9:46 am

coloin wrote:
Hud wrote:With two of ten coins of the heavier variety, I need 5 weighings to sort out the two copper ones


Yes this can always be done in five weighings.........12 again is the upper limit of the number of coins.

Only if the 2 heavier coins are of identical weights themselves... If you don't know if they are different or not (e.g. 1.02g and 1.01g compared to 1g), then you need more weighings...
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Postby underquark » Wed Jul 05, 2006 2:50 pm

You could atach lengths of fine thread to each coin and spin them from a central, rotating pole (like a bit of K'Nex, for instance) and note that the heavier ones don't orbit at quite the same altitude as the lighter ones. Some gearing is required to achieve the desired speed.
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Postby Hud » Wed Jul 05, 2006 9:32 pm

I have to reply to udosuk's post about the spelling of "sulphor".

Interestingly a few cities in USA are named Sulphur...


About 16 years ago, a good friend of mine's son got in with the wrong kind of crowd and he and a friend stole his car. They decided to head for Florida and got as far as Sulphor, Louisiana where they ran short of money and tried to skip out on a meal to save what cash they had left. They were arrested by the authorities and the kids were put in the pokey and the car was impounded. My friend told me about it, and I said I'd help him in any way I could. He came back and asked it I'd go back with him to recover the car. His son had been brought back by the authorities. I agreed and his insurance covered the expenses for the recovery. We flew from Phoenix to Lake Charles, LA, and rented a cab to Sulphor, LA. We tried to start the car (Mazda 626) I believe, and the battery was dead. We walked over a mile to a store and bought a new battery and walked back and installed it in the car. We left there in the evening, and started back to Arizona. In Texas, we ran into a fog bank and were lucky to have a van in front of us that was traveling at 80mph. I let him have enough room to see his taillights, but have room to stop if need be, I could have cried when he pulled into a rest area and we were on our own. We immediately had to slow to about 40mph, and that was too fast for the conditions. Eventually, we got behind a big rig and made decent time again. We made it back to Phoenis around 1pm next day with no further problem. After we got home, we noticed that one tire was almost flat. I suppose the tire didn't go flat due to the speed we were driving.
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