you have 9 coins, one of which is a different weight than the others. All look identical. How to determine which is the different coin with 3 weighings in a double pan balance.
2006-09-12 09:57:23 · 4 answers · asked by credo quia est absurdum 7 in Science & Mathematics ➔ Mathematics
3 groups of three. If the first two groups are balance then the overweght coin is not there. Then you can take the third group and put one coin on each side. If balance, you hold the overweight coin. If not balanced the the overweight coin is on the down side.
If the original groups of three are not balance, the do the second part of the first paragraph to group of three that is down.
2006-09-12 10:07:04 · answer #1 · answered by Anonymous · 0⤊ 0⤋
First, place four coins in one pan and four coins in the other pan. If they weigh the same, the ninth coin is the heavier/lighter coin. Second, take the heavier four coins and split them so two coins are in one pan the the other two coins are in the other. Third, take the heavier of the two coins and place one coin in one pan and place one coin in the second pan. You should have your answer. Then again, on the Second step, the lighter coins may have been the one to weigh in. Good Luck!
2006-09-12 17:10:51 · answer #2 · answered by icemountian8 3 · 0⤊ 0⤋
Weigh 3 vs 3
Balance
Odd one is in in 3rd group. So balance 1 against 1 in this group. If the same, then other coin is different. If imbalance, then balance 1 of them against another coin. If the same, then the other coin is different. If different, then this coin is the one.
Imbalance
Take 2 against 2.
Balance:
One of the others is different. Take one of them and balance against another coin. This will tell you if this coin of the other one is different.
Imbalance:
Balance one from each side. If balance => weigh one of the others against a known coin. If imbalance, then this is your coin. Otherwise the other coin is the one.
If imbalance, then weigh one of them against a known coin. This will tell you if this or the other coin is the one.
Hope this makes sense!
2006-09-12 17:13:34 · answer #3 · answered by Monty Burns 2 · 0⤊ 0⤋
you weigh four coins against four others, if the scales are even, then the ninth is the one you look for. if not, it is among the four in the lighter pan.
take those four and weigh one against one two times. on one weighing one of the pans will be lighter.
2006-09-12 17:06:48 · answer #4 · answered by wolschou 6 · 0⤊ 0⤋