What and how?

You are a cook in a remote area with no clocks or other way of keeping time other than a four minute sandglass timer and a seven minute sandglass timer (the kind you turn over – hourglass shaped). You do have a stove, however, with water in a pot already boiling. Somebody asks you for a nine-minute egg, and you know this person is a perfectionist and will be able to tell if you undercook or overcook the eggs by even a few seconds. What is the least amount of time it will take to prepare the egg? And how will you prepare it so that it is neither undercooked or overcooked?

Click here for the solution

The answer is 9 minutes. First, flip both hourglasses over and drop the egg into the water. When the four minute timer runs out, flip it again. When the seven minute timer runs out, flip it over. The egg has been cooking seven minutes. Now when the four minute timer runs out again after eight minutes flip the seven minute timer back over. Since the seven minute timer has been running only a minute between flips, there is a minute worth of sand left. And when that minute runs out, the egg will have been cooking for exactly nine minutes.

more riddles

3 words

Though small I am, yet, when entire,I've force to set the world on fire.Take off a letter, and 'tis clearMy punch will hold a herd of deer:Dismiss another, and you'll findI once contained all humankind.Spark, park, arkmore...

read more

Why?

A woman lives in a skyscraper thirty-six floors high and served by several elevators which stop at each floor going up and down. Each morning she leaves her apartment and goes to one of the elevators. Whichever one she takes is three times more likely to be going up...

read more

Arrange the whole pack

Take from the pack the thirteen cards forming the suit of diamonds and arrange them in this order face downwards with the 3 at the top and 5 at the bottom: 3, 8, 7, Ace, Queen, 6, 4, 2, Jack, King, 10, 9, 5. Now play them out in a row on the table in this way. As you...

read more

A word I know

A word I know,Six letters it contains,Subtract just one,And twelve is what remains.Dozensmore riddlesDonec rutrum congue leo eget malesuada. Vivamus magna justo, lacinia eget consectetur sed, convallis at tellus. Quisque...

read more