Alphonso and his sister Sadie are entering the airport to meet their mother when Sadie gasps in surprise and says to her brother, “You see that man in the crowd over there?”
Alphonso replies, “It’s Bernie. I don’t believe it. Let’s go introduce ourselves.”
Neither of them had ever met Bernie before. They’d never seen a picture or painting of him, nor was he a famous celebrity.
Alphonso was born as a twin, but he was separated from his twin brother at birth. Bernie is Alphonso’s identical twin, which is how Sadie was able to recognize him in the crowd.
This is kind of a cheat, because there are probably other possible explanations. But we can’t have everything :)
Suppose you have twelve eggs and a balance scale. All of the eggs are identical except for one whose only difference is its weight. Using the scale only three times, determine which egg is the odd egg out and whether it is heavier or lighter than the other eggs.
Weigh four against four. If they’re equal, weigh three of them against three you haven’t weighed. If they balance too, weigh the last remaining egg against any of the others to see if it is lighter or heavier. If the three suspects are heavier, weigh one of them against another and the one that goes down is it. If they balance the remaining suspect is heavy. Use the same process if they’re lighter. If the initial four vs four don’t balance, weigh two heavy eggs and a light egg against one heavy egg, one light one and a known normal egg. If they balance weigh the remaining two light eggs against each other. If they balance the unweighed heavy egg is the odd one out. If the side with two heavy eggs goes down weigh them against each other. If they balance it is the light egg on the other side. If the other side goes down it is either because of one heavy egg on that side or because the one light egg on the other side is lighter than the rest. Weigh one of them against a known normal egg to determine which is true.