There are several versions of counterfeit coin puzzles where it is necessary to find the counterfeit coin, or coins, from a number of weighings. Most of these puzzles assume you have balance type scales available with two pans, where one object can be weighed against another. In this puzzle you have a single scale only with just one pan, which will weigh just one object, or group of objects at a time. You have three bags with an unspecified number of coins in each bag. One of the bags consists entirely of counterfeit coins weighing 75 grams each; the genuine coins weigh 70 grams each.
Question: What is the minimum number of weighing operations you need to carry out before you can be certain of identifying the bag of counterfeit coins?
source: Philip Carter and Ken Russell
Linkback:
https://tubagbohol.mikeligalig.com/index.php?topic=22788.0