80% of People Fail To Solve This Easy Math Puzzle

5 min readNov 14, 2020

A professor walks into a room and gives her students the following three numbers:

2, 4, 6.

The professor then tells her students that the sequence of numbers follows a simple rule and that it’s the students’ job to discover the rule by providing the next number in the sequence.

Each time the students guess the next number in the sequence, the professor will then tell the students if the number they provided “follows the rule” or “does not follow the rule.”

The students can guess as many numbers as they want. However, they can only try to identify the rule once.

Before you read any further, go ahead and try to figure out the rule yourself.

Based on what you think the rule is, what do you think the next number in the sequence is?

Most students in the class said that 8 is the next number.

The professor replied, “Follows the rule.”

Most students then said that 10 is the next number.

The professor replied, “Also follows the rule.”

After suggesting a few more numbers that followed the rule, most students concluded that “the rule is to add 2 to the last number.”

The professor shook her head and said, “That is not the rule.”

If you thought this was the rule too, don’t worry. Most people get the rule wrong as well. In fact, only about one in five people figure out the rule on their first try.

So what’s the secret to figuring out the rule?

Well, it’s simple.

The students who figured out the rule on their first try simply had a completely different approach to solving this problem.

One student, for example, decided to test out what seemed like a bunch of random numbers.

The first number she tested out was “-2.”

The professor replied, “Does not follow the rule.”

The student then asked, “7?”

The professor replied, “Follows the rule.”

The student tried all sorts of numbers: -11, 10, 43.

But here’s the thing: she wasn’t just asking random numbers. Instead, she had an idea of what the rule was, and she was trying to find a flaw with it.

Once she found a rule that she could no longer find a flaw for, she said, “The rule is that the next number must be higher than the previous one.”

The professor replied, “Good job! That’s the rule!”

So what’s the difference between the successful students and the unsuccessful students?

The students who were unsuccessful at figuring out the rule simply believed they figured out the rule quickly and then immediately suggested numbers that confirmed their belief.

Because they suggested numbers that confirmed their belief, they became increasingly more confident that they were actually right.

As a result, all they did was confirm what they believed was the right rule, rather than actually trying to figure out what the right rule was.

This is what’s known as confirmation bias, which is our brains’ tendency to only seek out information that confirms what we already believe.

Unfortunately, confirmation bias is dangerous, because each time we confirm what we think we know, we close ourself off to other points of view.

The successful students, on the other hand, did the complete opposite.

Instead of trying to prove themselves right by suggesting numbers that comfirmed their hypothesis, they tried to find numbers that proved themselves wrong.

This may just seem like a simple approach to solving a math puzzle, but it’s such an important approach to have in life.

Whether it’s math puzzles, politics, or science, understand that it’s not enough to just say you’re open-minded to disconfirming evidence.

Instead, you actually have to go out and try to prove yourself wrong by consciously looking for disconfirming evidence.

Yes, it won’t feel good, but the point of proving yourself wrong isn’t to feel good. It’s to bring you one step closer to the truth.

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80% of People Fail To Solve This Easy Math Puzzle

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Written by Allblacksnzfog