math question?
You have 45 silver coins but one of them is a lighter weight counterfeit. How can you determin the counterfeit coin in a maximum of 3 weighings on a balance scale?
Related posts:
- Can you answer this math question? You have eight coins and a balance scare. The coins look alike, but one is counterfeit and lighter then the other seven. Find the counterfeit coin using two weighings on...
- Trivia Question..(Math Related)? Okay so here is the question. I need help finding the answer. *You have 3 coins and a pan balance scale. The coins are alike in appearance, but you know...
- Math trivia question? Out of 101 coins, 50 are counterfeit and differ from the original ones in weight by 1 gram. You pick a coin out of those 101 coins. You have a...
- Tricky Math Question!! HELP!? Steven has 9 cold coins that are identical that are identical in appearance. However, one is counterfeit and weighs slightly less than the others. Using a balance scale, how can...
- I have a math/logic question? If a guy has 9 gold coins and one is counterfeit (so it weighs a little less) and he’s only allowed to weigh it twice on the balance, how does...
I don’t think you can; I think it takes n=ceil(log(45)/log(3))=4:
#1: Weigh 15 on each side of the scale. If they weigh the same, put those 30 in your pocket and get the remaining 15. If they don’t, put the heavier 15 and the 15 you didn’t weigh in your pocket and get the lighter 15.
#2: Weigh 5 on each side; do the same thing to narrow the lighter coin to one of the groups of 5.
#3: Weigh 2 on each side. If they balance, the leftover is it; if not:
#4: Weigh the 2 of the lighter side against each other.