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

How does the man escape?

A man is trapped in a room. The room has only two possible exits: two doors. Through the first door there is a room constructed from magnifying glass. The blazing hot sun instantly fries anything or anyone that enters. Through the second door there is a fire-breathing...

read more

Five-digit number

What is the five-digit number, no zeroes, in which the second digit is three times the first, the third is one more than the second, the fourth is four times the first, and the last is one-half more than the second? The number is: 26789 more...

read more

The peanuts and the monkey

Five men checked into a hotel with a bag of peanuts and a monkey. They planned on dividing the peanuts evenly the following morning. However, during the night, one of the men got up, divided the peanuts into five equal parts, took his fifth and had one leftover peanut...

read more

How many children does Mr. Smith have?

Mr. Smith has 4 daughters. Each of his daughters has a brother. How many children does Mr. Smith have? He has 5 children, all of the daughters have the same 1 brother. more riddlesDonec rutrum congue leo eget malesuada....

read more