A maddening number puzzle designed by Japanese inventor Nob Yoshigahara has been doing the rounds on Reddit, baffling countless people with what at first appears to be a simple mathematical solution.
Nob, a noted puzzle designer in his homeland and author of puzzle games for periodicals, reportedly considered this creation, informally called Nob’s Number Tree, to be his “masterpiece.”
The puzzle’s design reveals a series of numbers floating in circles, with a single arrow emanating from each one pointing toward another circle, also suggesting the direction in which the puzzle unfolds.
To solve the puzzle, a contestant must discover the general “certain rule” governing the arrangement of numbers in order to successfully calculate the number that should appear instead of a question mark in one of the bubbles.
This maddening number puzzle designed by Japanese inventor Nob Yoshigahara has been circulating on Reddit, baffling countless people with what at first appears to be a simple mathematical solution.
Starting at the top left of the puzzle, there are two numbers: 99 and 72.
The arrows separated from bubbles 99 and 72 point to a third bubble, which contains the number 27.
Bubble 27 then points towards a bubble 18. When you move the cursor to the right, a bubble of the number 45 also points towards the same bubble of the number 18.
Then, an arrow points from bubble 18 to bubble 21. And, floating to the right, a bubble 39 also points to the same bubble 21.
At this point, someone might deduce that the solution is a matter of subtraction: 99 minus 72 equals 27. And 45 minus 27 equals 18. And 39 minus 18 equals 21.
Skipping the question mark bubble, the subtraction solution continues to make sense until you reach the trio of number bubbles at the bottom right.
Here, 21 and 13 equal seven, but 21 minus 13 equals eight.
At this point, one might begin to wonder if there really is a typo where the seven appears.
Nob is reportedly said to have considered the puzzle design, informally called “Nob’s Number Tree,” to be his “masterpiece.”
But the text next to the graphic insists: “The number seven in the final circle is not a typo.”
Dozens of Reddit users were stumped by the mystery. So what is actually the real key to solving the puzzle?
If one were to wrongly assume that the pattern is to find the difference between each of the two numbers pointing to a third bubble to find its value, then one would incorrectly calculate that, because the numbers 36 and 21 point to the question mark. bubble, that the question mark should be replaced by the number 15.
However, again, the number seven is not the difference between 21 and 13, thus refuting the hypothesis.
In fact, the trick is to add each of the individual numbers of the two bubbles that point to the third bubble to get the value of the third bubble.
For the first example, divide 99 and 72 so that it becomes a 9 + 9 + 7 + 2 addition problem, and the solution is again 27.
Then, looking at the 45 and 27 bubbles, imagine it as 4 + 5 + 2 + 7, which is also equal to 18.
For 39 and 18, add 3 + 9 + 1 + 8 and voila, you have 21.
And this works for the final trio of bubbles at the bottom right, with the numbers 21 and 13, calculate it as 2 + 1 + 1 + 3, and that does indeed equal seven.
And with this pattern, you can finally deduce the number from the question mark: taking 36 and 21, you add 3 + 6 + 2 + 1 and arrive at the correct solution.
The question mark is equal to the number 12.