Ten bags and one weigh is one of those puzzles where the way you ask the question matters more than the amount of calculations. The elegant solution does not multiply operations: it finds the idea that organizes the problem in a single action.
Ten bags and one heavy
Riddle statement
There are 10 bags of coins. In 9 of them, each coin weighs 10 g. In the remaining one, all the coins weigh 11 g.
You have only one weighing on a digital scale.
How do you identify the different bag?