99% Get This Math Puzzle Wrong… Can You Solve 1 + 1 × 1 + 1 + 1 × 0!? (See More)

At first glance, this looks like one of those ridiculously simple math problems that should take only a few seconds.

Every number is just 1.

There are no large numbers.

There are no complicated fractions.

And yet, this tiny equation can cause surprisingly long arguments online.

The expression is:

1 + 1 × 1 + 1 + 1 × 0! = ?

Some people immediately start adding the ones.

Others remember that multiplication comes before addition.

Then there's the strange-looking 0!, which can make the whole problem even more confusing.

So what is the correct answer?

Let's slow it down and solve it properly.

The First Trick: What Does 0! Mean?

The most unusual part of the equation is probably 0!.

The exclamation mark here doesn't mean excitement.

It represents the mathematical operation called a factorial.

A factorial means multiplying a whole number by every positive integer below it.

For example:

3! = 3 × 2 × 1 = 6

And:

2! = 2 × 1 = 2

But what happens with zero?

By definition:

0! = 1

This is an important mathematical rule.

So the final multiplication in our equation becomes:

1 × 0! = 1 × 1 = 1

Already, the expression is looking much simpler.

Now Follow the Order of Operations

The equation is:

1 + 1 × 1 + 1 + 1 × 0!

We first evaluate the factorial:

0! = 1

So we now have:

1 + 1 × 1 + 1 + 1 × 1

Next, multiplication must be performed before addition.

There are two multiplication operations.

The first is:

1 × 1 = 1

The second is:

1 × 1 = 1

So the expression becomes:

1 + 1 + 1 + 1

Now there are only additions left.

Add them together:

1 + 1 + 1 + 1 = 4

The Answer Is 4

So the mathematically correct answer is:

4

It isn't 2.

It isn't 3.

And the factorial symbol doesn't turn the entire expression into something dramatically different.

The key is simply understanding what 0! means and applying the standard order of operations.

Why Does 0! Equal 1?

This is the part that often surprises people.

Why would zero factorial equal one instead of zero?

Factorials follow a mathematical pattern.

For example:

4! = 24

3! = 6

2! = 2

1! = 1

To continue that pattern downward, we have:

1! = 1 × 0!

Since 1! equals 1, the equation becomes:

1 = 1 × 0!

Therefore:

0! = 1

This definition is also extremely useful in areas of mathematics involving combinations and permutations.

So although it may look strange at first, 0! = 1 is a standard mathematical result.

The “Answer Is NOT 2!” Detail

There's another little joke hidden in puzzles like this.

If an image says something such as “The answer is NOT 2!”

, the exclamation mark can have two different meanings.

In ordinary writing, the exclamation mark simply adds emphasis.

But in mathematics, 2! means “2 factorial.”

And:

2! = 2 × 1 = 2

So saying that the answer is “not 2!” can technically be read as saying:

The answer is not equal to 2 factorial.

Since the actual answer is 4:

4 ≠ 2

That statement is mathematically correct.

The wording creates a small extra layer of confusion.

Where Could Someone Get 2?

A person might look at the equation and mentally simplify it incorrectly.

Because there are so many ones, the expression can feel almost meaningless.

Someone might also misunderstand

0! and assume it equals zero.

If that happened, the last part would become:

1 × 0 = 0

That would produce a different result.

But factorial notation does not work that way.

The correct mathematical definition is:

0! = 1

That's why understanding the notation matters.

Don't Just Count the Numbers

One reason these puzzles are popular is that the numbers themselves look harmless.

There are several ones.

There is a zero.

And there are only addition and multiplication symbols.

It can therefore feel like a problem designed for elementary arithmetic.

But the equation is actually testing whether you recognize the symbols and apply the rules in the correct order.

The challenge isn't really the addition.

It's reading the expression correctly.

A Quick Way to Solve It

Whenever you see a similar expression, don't rush.

Look for special operations first.

Here, the order is:

Factorial → Multiplication → Addition

So:

0! = 1

Then:

1 × 1 = 1

and:

1 × 1 = 1

Leaving:

1 + 1 + 1 + 1 = 4

That's the entire solution.

Why These Puzzles Go Viral

Simple math puzzles are perfect for social media because almost everyone feels qualified to answer them.

You don't need advanced mathematics.

You don't need a calculator.

And because the equation looks so easy, people often answer immediately.

That creates the perfect recipe for disagreement.

One person comments “2.”

Someone else says “3.”

Another person insists the answer is “4.”

Then someone brings up PEMDAS.

Before long, a tiny equation has created hundreds of comments.

That's part of the fun.

Final Answer

After following the standard mathematical rules:

0! = 1

1 × 1 = 1

1 × 0! = 1

Therefore:

1 + 1 + 1 + 1 = 4

Final Answer: 4

So, did you get 4 immediately, or did the 0! make you stop and think for a moment?