The Quant 7522 / 75
HardBrain Teasers
12 Balls, One Odd
CitadelJane StreetTwo Sigma
12 identical-looking balls include exactly one of a different weight — you don’t know if it’s heavier or lighter. Using only a balance scale, what is the minimum number of weighings that guarantees finding the odd ball AND whether it is heavy or light?
Approach
Each weighing gives one of three results.
Count the possibilities you must distinguish: 12 × 2.
Sign in to reveal the full worked solution, check your answer instantly, and track your progress with spaced-repetition review.
Related problems
Screwy PiratesHardHorse Race — Top 3MediumSum 1 to 100Easy100 LockersMediumPoisoned WineMediumMislabeled JarsMedium
More in Brain Teasers.