You walk up to a mountain that has two paths. One leads to the other side of the mountain, and the other will get you lost forever. Two twins know the path that leads to the other side. You can ask them only one question. Except! One lies and one tells the truth, and you don't know which is which. So, What do you ask?
You ask each twin "What would your brother say?"
This works because.... Well let's say the correct path is on the left side. So say you asked the liar "What would your brother say?" Well, the liar would know his brother was honest and he would say the left side, but since the liar lies, he would say right. If you asked the honest twin the same question, he would say right, because he knows his brother will lie. Therefore, you would know that the correct path was the left.
You have two cups. One cup is filled with black coffee and another cup is filled with black tea. Both cups are filled with equal quantity of respective beverages. Take one spoonful of black tea and mix with the cup of black coffee. Then take one spoonful of black coffee and mix it with the cup of black tea.
Now tell, me which cup has more liquid in it? Does the cup of black tea has more liquid or black coffee has more liquid?
Both cups have equal quantity of respective drink. You take one spoonful from tea and mix it with coffee and vice versa.
