Iconic Japanese puzzle with mind-boggling mathematic solution leaves the internet baffled – but can YOU solve it?

An amazing number puzzle designed by Japanese inventor Nob Yoshigahara making the rounds on Reddit – confusing countless people with what seems like a simple mathematical solution.

Reportedly, Nob, a celebrated puzzle designer in his home country who wrote puzzle games for magazines, considered this creation, informally called Nob’s Number Tree, his “masterpiece.”

The layout of the brainteaser reveals a series of numbers floating in circles, with a single arrow pointing from each number to another circle, also suggesting the direction in which the brainteaser unfolds.

To solve the puzzle, a participant must discover the overarching ‘certain rule’ that determines the arrangement of numbers. This way he or she can calculate the number that should appear in place of a question mark in one of the bubbles.

Starting at the top left of the puzzle there are two numbers: 99 and 72.

Separate arrows from the 99 and 72 bubbles both point to a third bubble, which contains the number 27.

The 27 bubble then points to an 18 bubble. If you hover to the right, a bubble of 45 also points to the same bubble of number 18.

Then an arrow points from the 18 bell to a 21 bell. And floating to the right, a 39 bubble also points to the same 21 bubble.

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.

If we skip the question mark bubble, the subtraction solution continues to make sense all the way down, that is, until we get to the trio of number bubbles at the bottom right.

Here 21 and 13 both point to seven, but 21 minus 13 equals eight.

At this point you might be wondering if there is indeed a typo where the seven appears.

Nob reportedly considered the puzzle design, informally called Nob’s Number Tree, to be his “masterpiece.”

But the text next to the image emphasizes: “The number seven in the last circle is not a typographical error.”

Dozens of users on Reddit were puzzled. What is actually the key to solving the puzzle?

If you were to wrongly assume that the pattern consists of finding the difference between each of the two numbers pointing to a third bell to find its value, you would be wrong to assume that because the numbers 36 and 21 point to point the question mark. bell, that the question mark should be replaced by the number 15.

But again, the number seven is not the difference between 21 and 13, thus disproving the hypothesis.

Basically the trick is to add each of the individual numbers in the two bubbles pointing to the third bubble to get the value of the third bubble.

For the first example, you split 99 and 72 so that it becomes a 9 + 9 + 7 + 2 addition problem, and the solution is again 27.

Then look at the bubbles of 45 and 27 and imagine this as 4 + 5 + 2 + 7, which also equals 18.

For 39 and 18, add 3 + 9 + 1 + 8, and voila, you have 21.

And this works for the last trio of bubbles at the bottom right, with the numbers 21 and 13, calculate it as 2 + 1 + 1 + 3, and that is indeed equal to seven.

And with this pattern you can finally derive the number for the question mark: take 36 and 21, add 3 + 6 + 2 + 1 and you arrive at the correct solution.

The question mark is equal to the number 12.