Best long medium riddles

interviewlogicmath

Three ants are sitting at the three corners of an equilateral triangle. Each ant starts randomly picks a direction and starts to move along the edge of the triangle. What is the probability that none of the ants collide?
So let’s think this through. The ants can only avoid a collision if they all decide to move in the same direction (either clockwise or anti-clockwise). If the ants do not pick the same direction, there will definitely be a collision. Each ant has the option to either move clockwise or anti-clockwise. There is a one in two chance that an ant decides to pick a particular direction. Using simple probability calculations, we can determine the probability of no collision. P(No collision) = P(All ants go in a clockwise direction) + P( All ants go in an anti-clockwise direction) = 0.5 * 0.5 * 0.5 + 0.5 * 0.5 * 0.5 = 0.25
73.41 %
63 votes
cleanpoemswho am I

Two sisters we are, one is dark and one is fair, In twin towers dwelling we're quite the pair, One from land and one from sea, Tell us truly, who are we?
The answer is salt and pepper.
73.36 %
233 votes
logictricky

Swaff was traveling in an elevator, being cool, when he suddenly heard the cord supporting the elevator snap. Being the cool guy that he is, he knew of a myth where if you could jump at the right time, you could possibly be able to survive a plunge in an elevator. Now, when Swaff was a boy, he spent all of his math classes making fun of his female teacher's moustache. He never paid attention, so he was a tad bit slow in his mathematical calculations. He did, however, have a very bizarre talent, in which he could tell the exact speed he was traveling. That came in pretty lucky today. Swaff knew he was falling at an even rate of 50 miles per hour. When the cord snapped, he was exactly 110 feet above the ground. He knew that he must jump at the right time to have any hopes of surviving. Now, after doing the math, please tell me when Swaff jumped.
He never did. By the time Swaff figured out that he would have to jump in 1.5 seconds, he would already be dead. Not even the best of mathematicians could do all the math needed in 1 and half seconds. Swaff fell to his death.
73.31 %
49 votes
cleantrickycleverlogic

There are ten people in a house. Everybody wants to make a hand shake with only people shorter than themselves. Assume everybody is different in height. How many hand shakes are made?
0, because a taller person wants to shake hands with a shorter person. But the shorter person doesn't want to shake hands with him.
73.25 %
76 votes
logicmathclever

You can easily "tile" an 8x8 chessboard with 32 2x1 tiles, meaning that you can place these 32 tiles on the board and cover every square. But if you take away two opposite corners from the chessboard, it becomes impossible to tile this new 62-square board. Can you explain why tiling this board isn't possible?
Color in the chessboard, alternating with red and blue tiles. Then color all of your tiles half red and half blue. Whenever you place a tile down, you can always make it so that the red part of the tile is on a red square and the blue part of the tile is on the blue square. Since you'll need to place 31 tiles on the board (to cover the 62 squares), you would have to be able to cover 31 red squares and 31 blue squares. But when you took away the two corners, you can see that you are taking away two red spaces, leaving 30 red squares and 32 blue squares. There is no way to cover 30 red squares and 32 blue squares with the 31 tiles, since these tiles can only cover 31 red squares and 31 blue squares, and thus, tiling this board is not possible.
73.22 %
67 votes
logiccleverclean

Four people come to an old bridge in the middle of the night. The bridge is rickety and can only support 2 people at a time. The people have one flashlight, which needs to be held by any group crossing the bridge because of how dark it is. Each person can cross the bridge at a different rate: one person takes 1 minute, one person takes 2 minutes, one takes 5 minutes, and the one person takes 10 minutes. If two people are crossing the bridge together, it will take both of them the time that it takes the slower person to cross. Unfortunately, there are only 17 minutes worth of batteries left in the flashlight. How can the four travellers cross the bridge before time runs out?
The two keys here are: You want the two slowest people to cross together to consolidate their slow crossing times. You want to make sure the faster people are set up in order to bring the flashlight back quickly after the slow people cross. So the order is: 1-minute and 2-minute cross (2 minute elapsed) 1-minute comes back (3 minutes elapsed) 5-minute and 10-minute cross (13 minutes elapsed) 2-minute comes back (15 minutes elapsed) 1-minute and 2-minute cross (17 minutes elapsed)
73.12 %
80 votes
logicmathsimple

Every day, Jack arrives at the train station from work at 5 pm. His wife leaves home in her car to meet him there at exactly 5 pm, and drives him home. One day, Jack gets to the station an hour early, and starts walking home, until his wife meets him on the road. They get home 30 minutes earlier than usual. How long was he walking? Distances are unspecified. Speeds are unspecified, but constant. Give a number which represents the answer in minutes.
The best way to think about this problem is to consider it from the perspective of the wife. Her round trip was decreased by 30 minutes, which means each leg of her trip was decreased by 15 minutes. Jack must have been walking for 45 minutes.
73.05 %
71 votes
logictricky

A horse is tied to a fifteen-foot rope and there is a bale of hay 25 feet away from him. The horse however is still able to eat from the hay. How is this possible?
The rope wasn't tied to anything.
72.69 %
100 votes
trickylogic

A woman with no driver license goes the wrong way on a one-way street and turns left at a corner with a no left turn sign. A policeman sees her but does nothing... Why?
She is walking.
72.54 %
145 votes