[Thinking hard. Image courtesy of popsci.com]

The science, fantasy, and science fiction website io9 has a marvelous weekly feature run by Robbie Gonzalez, wherein they tackle brain teasers and riddles both new and old. I’ve explored several of them here on PuzzleNation Blog, most notably the 100 Men in Hats puzzle, which expanded on the Men in Hats puzzle concept from one of our earliest posts.

But one of their latest riddles provided a valuable example of how crucial test-solving and crowd-sourcing can be to a puzzle’s success.

The idea was simple enough: look at the numbers below, and determine what number should take the place of the question mark. The only guideline? The answer was NOT six.

I posted this riddle on our Facebook page on Monday and shared it with fellow editors at the PuzzleNation office, and got all sorts of answers in return.

One solver came up with 5 as the answer, positing that the vertical numbers formed fractions. So, with 1/2 and then 3/4 as the next number, the pattern would be adding 1/4. Adding 1/4 to 3/4 equals 1, and 5/5 equals 1.

There were other solutions that also yielded 5 as an answer, like doing what my friend called a zigzag equation, adding 1 from the top to 4 from the bottom to get 5 on the top as the answer, and then reversing it by adding 2 from the bottom to 3 from the top, getting 5 on the bottom as the missing answer.

A second solver came up with 3 as the answer, adding the top row to equal 9, and then trying to do the same with the bottom row.

Another solver saw them as two separate patterns, where going from 1 to 3 involved adding 2 and going from 2 to 4 involved multiplying by two. Therefore, by this method, the answer is 8. (Yet another solver did the same, except they squared the numbers along the bottom row, leading to 16 as the answer.)

As you can see, there were all sorts of mathematical solutions. When you’re told to ignore the most obvious solution, your mind can create some truly innovative ways of reimagining the information available.

[A head full of numbers. Image courtesy of equip.org]

Several solvers thought outside the box and came up with R, relating the numbers by their positions on a gearshift knob instead of mathematically.

As it turns out, this was the solution the puzzle’s creator initially intended, only realizing later that the puzzle had many possible solutions.

In his own words: *The riddle was too open-ended. Whether you interpreted it as a mathematical puzzle, or an automotive design puzzle, it was poorly posed, and that’s on me. Puzzle-posing is an art in and of itself, and it’s easy to mess up. For a solution to be satisfying, the person posing the puzzle needs to provide enough information that the puzzle is unambiguously solvable, but not so much that it gives too much away.*

[A proposed layout that points more directly toward the creator’s intended solution.]

Now, as a puzzler myself, I can absolutely empathize with Mr. Gonzalez here. There are plenty of times I’ve created a puzzle or a brain teaser and assumed that everyone would follow the same path I envisioned, considering the solution if not obvious, then at least reproduceable.

But solvers can always surprise you by finding alternate routes to the answer or utilizing a different way of thinking that ends with a second, but still valid solution.

So after a few stumbles and missteps of my own in the past that were similar to the one in today’s puzzle, I now make sure to have another set of eyes on my brain teasers, either during the creation process or as a test-solver afterward.

A second set of eyes can be absolutely invaluable in helping you spot possible alternate solutions.

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