Best riddles

logic

A Fox, a sheep, and a sack of hay

A farmer is travelling with a fox, a sheep and a small sack of hay. He comes to a river with a small boat in it. The boat can only support the farmer and one other animal/item. If the farmer leaves the fox alone with the sheep, the fox will eat the sheep. And if the farmer leaves the sheep alone with the hay, the sheep will eat the hay. How can the farmer get all three as well as himself safely across the river?
The farmer takes the sheep across the river, then returns back. The farmer takes the fox across the river. The farmer takes the sheep back to the first side of the river. The farmer leaves the sheep back on the first side of the river, and takes the hay to the other side. The farmer returns to the first side of the river. The farmer brings the sheep back to the second side.
93.84 %
41 votes

interviewlogicmath

Crossing the Bridge Puzzle

Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?
It is 17 mins. 1 and 2 go first, then 1 comes back. Then 7 and 10 go and 2 comes back. Then 1 and 2 go again, it makes a total of 17 minutes.
93.84 %
41 votes

interviewlogicmath

Burning Rope Problem

A man has two ropes of varying thickness (Those two ropes are not identical, they aren’t the same density nor the same length nor the same width). Each rope burns in 60 minutes. He actually wants to measure 45 mins. How can he measure 45 mins using only these two ropes. He can’t cut the one rope in half because the ropes are non-homogeneous and he can’t be sure how long it will burn.
He will burn one of the rope at both the ends and the second rope at one end. After half an hour, the first one burns completely and at this point of time, he will burn the other end of the second rope so now it will take 15 mins more to completely burn. so total time is 30+15 i.e. 45mins.
93.84 %
41 votes

cleanlogic

Smartest kid in the world

Jake and his friend Paco had very famous challenge sessions at their school. One would suggest something they could do, and the other would prove it wrong somehow. One day, Jake surprised Paco by stating: "I can answer any question in the world." Sure that he would win the challenge, Paco accepted the task of proving it wrong. He wrote up a test full of impossible questions. After a while, Jake returned the test. Paco unbelievably lost the challenge and told Jake he could indeed answer any question. How did Jake win?
For all the impossible questions, Jake simply wrote "I don't know".
93.84 %
41 votes

logicmath

A grandfather's clock

A grandfather's clock chimes the appropriate number of times to indicate the hour, as well as chiming once at each quarter hour. If you were in another room and hear the clock chime just once, what would be the longest period of time you would have to wait in order to be certain of the correct time?
You would have to wait 90 minutes between 12:15 and 1:45. Once you had heard seven single chimes, you would know that the next chime would be two chimes for 2 o'clock.
93.84 %
41 votes

logic

Government School Inspector

Last week, the local Primary school was visited by the Government School Inspector who was there to check that teachers were performing well in their respective classes. He was very impressed with one particular teacher. The Inspector noticed that each time the class teacher asked a question, every child in the class put up their hands enthusiastically to answer it. More surprisingly, whilst the teacher chose a different child to answer the questions each time, the answers were always correct. Why would this be?
The children were instructed to ALL raise their hands whenever a question was asked. It did not matter whether they knew the answer or not. If they did not know the answer, however, they would raise their LEFT hand. If they knew the answer, they would raise their RIGHT hand. The class teacher would choose a different child each time, but always the ones who had their RIGHT hand raised.
93.84 %
41 votes

logicshort

Workers strike

This is a newspaper headline: Workers Strike - Want to Make Less Money! What is going on?
The workers work at the mint and are tired of being overworked. They want to work less, which is making less money, since money is made at the mind!
93.84 %
41 votes