Brain Teasers

Take a break for a moment and stretch your brain!

Below are a few moderately challenging brain-teasers and lateral thinking puzzles for your mental break. This section is updated with new challenges.  If you have questions or a “challenge” you would like to contribute (and get credit for), please send it to us (with the solution) to


The Marble Challenge: (Contributed by Daniel Sac from Beverly, MA)

In Figure 1 below, there are 5 containers, all full of marbles. Only one of the jars is full of 9 gram marbles, the rest of the jars are full of 10 gram marbles. All the marbles look and feel alike. You have only 1 weighing (reading) on a digital scale to determine which of the containers holds the 9 gram balls. This can be done, do you know how? Remember you only get 1 reading on the scale.




The Magic Triangle:

In figure 2 below, both the top and bottom figures have exactly the same 4 elements in it.  The identical parts are moved around to form the bottom figure, but mysteriously there is a newly formed “hole”.  Where does the hole come from?  Isn’t it mathematically and geometrically impossible?  Note:  There is a perfectly logical and rational explanation for the hole.  No tricks here.


Are you thinking straight? 5 questions:

  1. Mary’s father has five daughters: 1. Nana, 2. Nene, 3. Nini, 4. Nono. What is the name of the fifth daughter?
  2. What is the next letter in the following sequence?  W, I, T, N, L, I, T, F, ?
  3. What number written in English capital letters with all straight lines, represents the number of segments it contains?  For example, FIVE, which does not describe itself, contains 10 segments?
  4. A boat has a ladder that has six rungs, each rung is one foot apart. The bottom rung is one foot from the water. The tide rises at 12 inches every 15 minutes. High tide peaks in one hour. When the tide is at it’s highest, how many rungs are under water?
  5. What is the significance of the following: The year is 1978, the time is thirty-four minutes past noon on May 6th.



Bruce’s 3 dogs: (Contributed by Jeff Clinter from St. Claire, MI)

Brian & Bruce, two brothers that haven’t seen each other in a while, are walking down Westbrook street.  They start talking about Bruce’s newly aquired “best friends”.  The conversation goes like this:

3 dogs

  • Brian asks Bruce; “How old are your dogs?”
  • Bruce, who works for the department of justice and never liked to answer any question directly anyway, snickered and said; “Well, the product of their ages is 36.”
  • Brian, having just studied a lot of applied math to pass his builders test quickly said; “That’s not enough information”
  • Bruce points and replies; “OK, I’ll give you another hint.  The sum of their ages is the address of that house across the street.”
  • Brian, intrigued, thinks about it and replies; “I see that address, but that is still not enough information”
  • Bruce says; “OK, my last hint is that my oldest dog had a bad case of fleas last year.”
  • Brian, having all the information he needed confidently grinned and said, “Ahh, now I know each of their ages”

Question 1:  What are the ages of all three of Bruce’s dogs?
Question 2:  What was the address of the house Bruce pointed at across the street?