Authors: Folklore
There are 13 pupils in the school of witchcraft and wizardry. Before the Clairvoyance exam, the teacher put them at a round table and asked to guess who would receive the clairvoyant’s diploma. The students said nothing about themselves and two of their neighbours, but they wrote the following about all of the others: “None of these ten will get the diploma!" Of course, all of those who passed the exam guessed correctly, and all of the other students were mistaken. How many wizards received a diploma?
Find the largest number of colours in which you can paint the edges of a cube (each edge with one colour) so that for each pair of colours there are two adjacent edges coloured in these colours. Edges are considered to be adjacent if they have a common vertex.
In an attempt create diversity the government of the planet hired \(100\) truth tellers and \(100\) liars. Each of them has at least one friend. Once exactly \(100\) members said: “All my friends are honest” and exactly \(100\) members said: “All my friends are liars.” What is the smallest possible number of pairs of friends, one of whom is honest and the other a liar?
A class contains 33 pupils, who have a combined age of 430 years. Prove that if we picked the 20 oldest pupils they would have a combined age of no less than 260 years. The age of any given pupil is a whole number.
Specify any solution of the puzzle: \(2014 + YES =BEAR\).
Of five coins, two are fake. One of the counterfeit coins is lighter than the real one, and the other is heavier than the real one by as much as the lighter one is lighter than the real coin.
Explain how in the three weighings, you can find both fake coins using scales without weights.
A traveller met five inhabitants of the planet of liars and truth tellers. To his question: “How many truth tellers are there among you?” the first replied: “None!", and another two answered: “One.” What did the final two say?
The sheikh spread out his treasures in nine sacks: 1 kg in the first bag, 2 kg in the second bag, 3 kg in the third bag, and so on, and 9 kg in the ninth bag. The insidious official stole a part of the treasure from one bag. How can the sheikh work out from which bag the official stole the treasure from using two weighings?
The height of the room is 3 meters. When it was being renovated, it turned out that more paint was needed on each wall than on the floor. Can the area of the floor of this room be more than 10 square meters?
Author: D.V. Baranov
Vlad and Peter are playing the following game. On the board two numbers written are: \(1/2009\) and \(1/2008\). At each turn, Vlad calls any number \(x\), and Peter increases one of the numbers on the board (whichever he wants) by \(x\). Vlad wins if at some point one of the numbers on the board becomes equal to 1. Will Vlad win, no matter how Peter acts?