Can you solve the counterfeit coin riddle? - Jennifer Lu - YouTube
101 Coins Puzzle - One coin is fake - Is it heavier or lighter ? - YouTube
Privacy and Counterfeit Coins - Scientific American
Weighing Designs to Detect a Single Counterfeit Coin
EnjoyAlgorithms - 𝗔𝘀𝗸𝗲𝗱 𝗶𝗻 - Google, Microsoft, Amazon, Bloomberg. Yes, we can solve it in 2 weighings. Here is the solution idea - From the given coins, select two groups of three