Brain Teasers

One day, a father went to his three sons and told them that he would die soon and he needed to decide which one of them to give his property to. He decided to give them all a test. He said, "Go to the market, my sons, and purchase something that is large enough to fill my bedroom, but small enough to fit in your pocket." From this, I will decide who of you is the wisest and is worthy enough to inherit my land." So, they all went to the market and bought something that they thought would fill the room, yet was still small enough that they could fit into their pockets. Each son came back with a different item. The father told his sons to come into his bedroom one at a time and try to fill up his bedroom with whatever they had purchased. The first son came in and put some pieces of cloth that he had bought and laid them end to end across the room, but it barely covered any of the floor. Then the second son came in and laid some hay, that he had purchased, on the floor but there was only enough to cover half of the floor. The third son came in and showed his father what he had purchased and how it could fill the entire room yet still fit into his pocket. The father replied, "You are truly the wisest of all and you shall receive my property." What was it that the son had showed to his father?

Some will use me, while others will not, some have remembered, while others have forgot. For profit or gain, I'm used expertly, I can't be picked off the ground or tossed into the sea. Only gained from patience and time, can you unravel my rhyme? What am I?

There are three crates, one with apples, one with oranges, and one with both apples and oranges mixed. Each crate is closed and labeled with one of three labels: Apples, Oranges, or Apples and Oranges. The label maker broke and labeled all of the crates incorrectly. How could you pick just one fruit from one crate to figure out what’s in each crate?

Three cars had driven into a parking lot at the same time, and the three drivers left them all for the attendant to park. Unfortunately, he isn't too good at remembering exactly which driver drove which car. However, he is sure of these 6 facts:

a. Colin drove the BMW if and only if Mr. Cooper drove the Avenger.
b. Alan drove the Cortina if and only if Mr. Cooper drove the BMW.
c. Colin is Mr. Brown if and only if Mr. Andrews drove the BMW.
d. Brian is Mr. Andrews if and only if Colin drove the BMW.
e. Mr. Cooper drove the Avenger if and only if Alan is Mr. Brown.
f. Colin is Mr. Brown if and only if Alan drove the Cortina.

Who arrived with which car?

Picture three boxes containing fruit. The first box is marked peaches, the second is marked oranges, and the third box is marked peaches and oranges. Each of the boxes is labeled incorrectly. How could you label each box correctly if you were allowed to select only one fruit from one of the boxes?

Alice is walking throught the forest of forgetfulness. She wants to know what day of the week it is. She stops and asks a lion and a unicorn. Now the lion lies all of the time on Monday, Tuesday, and Wednesday. The unicorn always lies on Thursday, Friday and Saturday. Alice asks the lion what day it is, he says, "Well, yesterday was one of my lying days." Alice can't figure it out just from the lion's answer so she asks the unicorn and the unicorn says, "Yesterday was also one of my lying days." What day is it?

John noticed that the amount he was paying for his lunch was a rearrangement of the digits of the amount of money he had in his pocket, and that the money he had left over was yet another rearrangement of the same three digits! How much money did John start with?

I have a calculator that can display ten digits. How many different ten-digit numbers can I type using just the 0-9 keys once each, and moving from one keypress to the next using the knight’s move in chess? (In chess, the knight move in an L-shape – one square up and two across, two squares down and one across, two squares up and one across, and other like combinations)

You’re standing in a hallway with three light switches on the wall, each of which turns on a different lamp inside a closed room. You can’t see inside the room, and you can’t open the door except to enter the room. You can enter the room only once, and when you do, all the lamps must be turned off. How can you tell which switch turns on which lamp?

There are three bags, each containing two marbles. Bag A contains two white marbles, Bag B contains two black marbles, and Bag C contains one white marble and one black marble. You pick a random bag and take out one marble, which is white. What is the probability that the remaining marble from the same bag is also white?