MathDB
Guessing a number

Source: St Petersburg 2008 10th grade #4

July 28, 2011
number theory proposednumber theory

Problem Statement

A wizard thinks of a number from 11 to nn. You can ask the wizard any number of yes/no questions about the number. The wizard must answer all those questions, but not necessarily in the respective order. What is the least number of questions that must be asked in order to know what the number is for sure. (In terms of nn.)
Fresh translation.