There are 3 coins. All of them look the same. Exactly 1 coin is counterfeit, and it is lighter than a true coin.
All true coins weigh the same amount.
You may use a set of balance scales.
Can you isolate the counterfeit coin with only 1 weighing?
Exactly 1 of these 3 coins is counterfeit, and it is lighter. Use 1 weighing to isolate it.
Try a direct comparison first. A good weighing should split the three cases as evenly as possible.
Left pan
Drop coins here
Right pan
Drop coins here
Coin tray
Drag coins from here onto either pan
Preview = case split; tap coins to move tray ↔ pans.
3 cases match history.
Pick the fake from the full set of coins.
Sign in or create an account to reveal answers, view the solution, and save your progress. Create a free account to unlock practice and keep track of your work.
One puzzle per day. Cryptarithm, Magic Square, Summit. No sign-up required to play.
Play daily puzzle →Interactive problems and curated lessons—water pouring, magic squares, knight's tour, and more.
Browse library →See how you rank. Top solvers by problems solved correctly. Sign in to climb the ranks.
View leaderboard →