10 prisoners share a cell. The prison warden tells them that the next day they’ll be randomly lined up for execution. He’ll place either a black or white cap on everyone’s head. Each prisoner starting from the back of the line will guess what color his hat is. If he gets it wrong he’ll be executed. Every prisoner can not see the hat on his head or of those behind him. He can see the hats of everyone in front of him. How can the prisoners devise a strategy to save their lives? You can find the solution here .
Image from: Popular Mechanics By now you might have heard many, many, many puzzles of some people always telling truth, and others always telling lies. But in real life, we all neither knights, nor knaves. Anyway this puzzle is slightly different - there are couples and these couples both lie or both tell truth or one lies and other one tells truth. (We all like to believe ourselves to be the last one - wink wink) Dags, Eggs and Fens are being interrogated as one of them is a spy. One of the couples always tells truth. In another couple, both husband and wife always lie. And in the third couple, one of the spouses always lies and the other one always tells truth. Here are the statements by the three couples when interrogated. Mr. Dag: I am not the spy Mrs. Dag: Mr. Egg is the spy. Mr. Egg: Mr. Dag is truthful. Mrs. Egg: Mr. Fen is the spy. Mr. Fen: I am not the spy. Mrs. Fen: Mr. Dag is the spy. Which person is a spy? (This puzzle is take...
A scale is balanced. On one side of the scale, there are 3 1 ⁄ 2 bags of rice and on the other side there are 1 3 ⁄ 4 bags of rice and 1 ⁄ 4 kilo weight. What is the weight of one bag of rice? This puzzle is borrowed from the book "Brain teasers" by Ian Livingstone and Jamie Thomson Show answer Let the weight of 1 bag of rice be b. So 3 1 ⁄ 2 b = 1 3 ⁄ 4 b + 1 ⁄ 4 Transferring 1 3 ⁄ 4 b to LHS we get 1 3 ⁄ 4 b = 1 ⁄ 4 b = 1 ⁄ 4 / 1 3 ⁄ 4 = 1 ⁄ 7 kg
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