Riddle Me This!

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Think you're good at riddles? What about math? Below are some enigmas of my own design and a couple variations on classic puzzles. I start off with a couple of simple ones and progressively raise the bar.

Answer all five riddles/puzzles OR the bonus problem correctly and I will donate $200 to your favorite top-rated charity. Answer them all correctly and I will donate $500 in your name.

No, the last two where I provide a solution don't count.

BRUCE HURLEY'S "FOUR COINS" PUZZLE = = = = = = = = = = = = = = = =

I don't know if this one's difficult or simple, but it came to me when I was fiddling with some coins while I was on hold.

You have four identical coins and a flat surface--nothing else. Without just "eyeballing" it, how can you arrange three of the coins so that they form a perfectly straight line?

You can't use the edge of the table and the coins have to lie flat.


BRUCE HURLEY'S "BROTHER'S AGE" RIDDLE = = = = = = = = = = = = = = = =
Yesterday, Bill was exactly one year older than his youngest brother. Today, he is exactly three years older than his youngest brother. How is this possible?

Also, how old is Bill exactly?

Click on the icon at right for a hint.


BRUCE HURLEY'S "ATHEIST AUTHOR" RIDDLE = = = = = = = = = = = = = = =
A publisher contracts with an author to write a book about religion. As an atheist, the author's values prohibit him from capitalizing the word "God," but his publishers insist that he do just that.

After some thought, he figures out a way to do what his publishers ask without compromising his principles. When the book is written, it appears as normal as any other book on religion (i.e. not in ALL CAPS or in another language, etc.), and the actual word in question appears hundreds of times. Yet the author and his publishers are both happy.

How does he do it?


BRUCE HURLEY'S "YELLOW AND GREEN" RIDDLE = = = = = = = = = = = =
After visiting with friends in St. Louis, I was driving to Colorado in the middle of the day. I was surrounded by a crop on both sides of the road.

When I looked to my right, I saw almost nothing but yellow. When I looked to my left, almost nothing but green. And yet, just a single crop was being grown.

How can that be?

Hint: The crop had been planted all at the same time and received all the same treatment.


GAME SHOW RIDDLE = = = = = = = = = = = = = = = = = = = = = = =
This confounding riddle is a more palatable variation of a conundrum posed by one of my heroes, mathematician Martin Gardner, in 1959. Gardner is one of the great minds of our times.

You are a contestant on a game show. The game is very simple. There are three doors: door #1, door #2, and door #3. Behind one door is a million dollars. The other two doors contain worthless joke prizes. All you have to do is pick which door you want to open, and you get whatever is behind it. But you only get to open one door. By simple math, then, you obviously have a 1 in 3 chance of picking the correct door and becoming an instant millionaire.

You pick a door. As soon as you tell the game show host what door you want to open, he stops and says, "Okay, you've made your choice. Now, I'm going to do what we always do here on this game. I'm going to open one of the other two doors for you that I know has a booby prize." And he does so.

Then he asks, "Okay, now, would you like to stay with your original guess, or would you like to switch to the other door that's still closed?You only get one shot, so do you want to stay with your original choice, or switch?"

Is there any compelling reason to switch doors if you want to win the million dollars?

Explain your answer mathematically (no formulas required).

To be clear, there is no trickery, and the host is not cheating. Furthermore, the money has not moved, will not be moved, and if you open the right door, you win the cash. Money is either behind the door you first picked, or behind the remaining unopened door.


BRUCE HURLEY'S "ROCK BAND PROBLEM" = = = = = = = = = = = = = = = =
Below is an algebraic problem I designed for a young friend of mine who had to pay a dear price for her failure to accomplish a certain goal. For anyone solving this problem, I will donate $200 in your name to the top-rated charity of your choice.

A group of students are trying to pick which of two Christian bands should play at regional dance they've organized. They're going to have a vote to decide the issue. The two bands are Prayer Jam and Fish.

To help the students decide which band to vote for, they had a mini-concert in which each band played three songs. After the concert was over, some people decided to change their preferences.

One-third of those who initially liked Prayer Jam decided to support Fish. And one-fourth of those who originally liked Fish now would vote for Prayer Jam.

When the votes were counted, everybody was surprised. It was a tie!

There are fewer than 250 students in total, and the ratio of male to female voters was 7:6.

How many students voted in the band decision?

Provide proof of how you solved it.

Extra Credit: If the election had taken place before the mini-concert, which band would have won and by how many votes?


  • This page about relative prime numbers may be of some help, although I can't promise anything.
  • This problem is really more about ratios than algebra.


The Extra Man Riddle= = = = = = = = = = = = = = = = = = = =
(as spread around the Web)

What happens to the extra man? CLICK HERE to find out.


AGE BY CHOCOLATE = = = = = = = = = = = = = = = = = = = =

Your Age By Chocolate
(as spread around the Web)

  • First of all, pick the number of times a week that you would like to have chocolate (more than once but less than 10).

  • Multiply this number by 2 (Just to be bold).

  • Add 5 (for Sunday).

  • Multiply it by 50.

  • If you have already had your birthday this year add 1754....If you haven't, add 1753.

  • Now subtract the four digit year that you were born.

You should have a three-digit number. The first digit of this was your original number (i.e., how many times you want to have chocolate each week). The next two numbers are:


The Explanation You Really
Don't Want To Read

If you think mathematical riddles like this are amazing and magical, it's probably best that you don't read this explanation (solution). Ask any magician: everybody says they want to know how a trick is done, but they're almost always disappointed when they find out. If you really want to know how it's done, it will be a lot more satisfying if you figure it out for yourself.

Age by Chocolate Solved

Contact me if you have any questions.