Tetrahedron puzzle

Consider a regular tetrahedron with an edge length of 3 units. A regular polyhedron with faces, vertices and edges is made by cutting a regular tetrahedron with an edge length of one unit from each of the 4 corners of the tetrahedron .

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Currency exchange

To go on holiday Peter converts 300 euros into US dollars. Had he bought three months earlier he would have received the same number of dollars for 50 euros less, since the rate of exchange was two dollars to the euro more then than on the day he bought them.

soft-boiled egg

The 9-minute egg

You are a cook in a remote area with no clocks or other way of keeping time other than a four minute hourglass and a seven minute hourglass. You do have a stove however with water in a pot already boiling.

three sisters

Three daugthers

A man in my neighborhood has three daughters. One day when I asked their ages he said, “The product of their ages is 36.” When I still couldn’t find their ages he said, “Ok. I’ll give you another clue: the sum of their ages is same as the number of my house.”


3, 3, 7, 7 = 24?

Can YOU solve this fiendishly difficult math problem? 95% of MIT students CANNOT and only 10% of Stanford students CAN! Here it is: Can you make the number 24 from using 3, 3, 7, 7? And here are the rules: you have to use ALL the numbers but once only.

music band

The five musicians

Dave, Simon, Jason, Helena and Zoe are all musicians who play a different instruments from the following list: violin, oboe, percussion, flute and clarinet. Jason, Zoe, Simon and the flute player all live in the same city. The clarinet player enjoys spending time with Jason, Simon and Dave, but he really dislikes the oboe player.


Simpson’s paradox

Simpson’s paradox is a classic puzzle discussed in introductory statistics courses worldwide. That is, when confronted with a Simpson’s paradox, where two different choices seem to compete for being the best choice depending on how the data is partitioned, which choice should one choose?

three prisoners problem

The three prisoners

Three prisoners are in separate cells and are all sentenced to death. The governor selected one at random to be pardoned. The guard knows who is going to be pardoned but won’t say.


Bertrand’s box paradox

I have three boxes, each with 2 compartments. One has two gold bars, one two silver bars and one has one gold and one silver bar. You choose a box at random and open a compartment at random.

water heater

Conjunction fallacy

“Last week, the heat in my apartment crapped out because my water heater broke. I went to a person, showed him the water heater, he used a bunch of spare parts and then fixed it. I paid him for the repairs.”