Water. As ice I’m hard and cold, as water vapor I’m hard to hold and I’m always present in the air as humidity (aka water vapor). If the earth ever runs out of water, we’re toast.
On a remote (imaginary) island, there are 11 snakes and a single mouse. As you’d expect, snakes eat the mice. But contrary to what you’d expect, when a snake eats a mouse, it turns into one.
The snakes live by only two rules:
1. Don’t get eaten. 2. Eat mice as long as rule #1 isn’t violated.
How many snakes and mice will there be left on the island?
You are a prisoner sentenced to death. The Emperor offers you a chance to live by playing a simple game. He gives you 50 black marbles, 50 white marbles and 2 empty bowls and instructs you to divide the 100 marbles into the two bowls. You can divide them however you want as long as all the marbles are in the bowls. You will be blindfolded and the bowls and marbles will be thoroughly mixed. You will then choose a single marble from one of the bowls. If the marble is white, you live. Black and you will be put to death.
How do you divide the marbles up so that you have the greatest probability of choosing a white marble?
Place one white marble in one bowl and place the rest of the marbles in the other bowl (49 whites, and 50 blacks).
This way you begin with a 50/50 chance of choosing the bowl with one white marble and living. Even if you choose the other bowl, you still have an almost 50% chance of picking one of the 49 white marbles. There are no guarantees in life, but this gives you the best change of surviving.