AdvancedNumeric answer
A balance, and coins of which exactly one is counterfeit and either heavy or light. What is the largest number of coins for which three weighings could possibly suffice, counting cases alone?
Answer with a number. Fractions, powers and expressions like 23/6 or C(52,5) are read correctly in practice.
The worked solution is in Premium
The answer, the full working and the one idea to take away – for this and all 1,322 questions in the bank. Answer it in practice and your working is marked, with a known mistake named when you make one.
Learn the method
Reported in interviews at
More games, decision theory and puzzles questions
- What is the angle, in degrees, between the hour and minute hands of a clock at 3:15?Foundation
- You have two eggs and a 100-storey building.Applied
- A hundred closed doors.Applied
- Four people must cross a bridge at night with one torch.Applied
- One of 1000 bottles of wine is poisoned, and the poison kills within a day.Applied
- Five pirates in strict seniority split one hundred coins.Advanced