Skip navigation


Think you’re smart? Try these brainteasers that recruiters use in actual job interviews.

This Month’s Contest: HOTTER-COLDER  

You have three identical flasks. Flask A contains one quart of 80-degree water; flask B contains one quart of 20-degree water; flask C is empty. You also have empty container D, which fits into any flask and has perfectly conducting walls (the contents of D will immediately be the same as the temperature of the water surrounding it).

The challenge: What is the simplest process to heat the cold water with the aid of container D and the hot water so that the final temperature of the cold water will be higher than the final temperature of the hot water?   

Rules: the only thing you can’t do is mix hot water into cold water. Assume no heat loss.

Please e-mail your solution to John Kador at [email protected] using the subject line “Hotter-Colder.” Deadline is Jan. 2, 2013. One entrant with the correct answer (or a creative alternative) will receive a signed copy of John Kador’s  How to Ace the Brainteaser Job Interview. Good luck to all.

Brainteaser #2: SPELL THAT NUMBER   

What is the only number that is spelled with all of its letters in alphabetical order in the English language?

Extra credit: What is the only number that has all of its letters in reverse alphabetical order?

This is a good puzzle to try at parties. Solution below.

Solution to previous puzzler: On Account 

To recap: An advisor has four clients: Arnie, Bob, Charlie, and Diane. The values of the portfolios are as follows: $5 million, $3 million, $2 million, and zero. The clients make the following statements. Arnie: My portfolio and Charlie’s are the biggest and smallest. Bob: My portfolio and Arnie’s have a total of $5 million. Charlie: If you subtract what’s in Diane’s portfolio from mine, you get $3 million. Diane: Neither I nor Arnie have the biggest or smallest portfolios. Two of these statements are lies. Which client has the most money in his or her portfolio?

Solution: Charlie is telling the truth that he has $5 million.


In a first for the REP. Puzzler, every submission we received had the correct solution. The random winner is Brooke Poskin of Securian Financial Services Inc., Renaissance Financial Corporation, Leawood, Kansas. Here’s her solution: 

After trying several combinations, there are only two combinations where both statements hold true—Arnie and Charlie or Charlie and Diane. In the scenario of Arnie and Charlie’s statements being true, Arnie has zero and Charlie has $5 million. If you subtract Diane’s $2 million from Charlie’s $5 million, you get $3 million. In the scenario of Charlie and Diane’s statements being true, if you subtract Diane’s $2 million from Charlie’s $5 million, you get $3 million. Neither Diane nor Arnie have the largest or smallest portfolios—Diane has $2 million and Arnie would be assumed to have $3 million. Either scenario that holds true—Charlie has the most money and is being honest (maybe that’s why he has the most money-there’s something there!).

Congratulations to Brooke, who will receive a signed copy of my book How to Ace the Brainteaser Job Interview.


Solution to Spell That Number:  The only number in English whose letters are in alphabetical order is forty. Extra credit: The only one whose letters appear in reverse alphabetical order is one. 


John Kador is the author of 10 books. His latest book is Effective Apology: Mending Fences, Building Bridges, and Restoring Trust (Berrett-Koehler).

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.