In case you don’t know, arithmetic is just taking 2 or more numbers and adding, subtracting, multiplying, dividing, etc. with them.

It looks like so:

`1 + 2 * 5`

The answer is:

`11`

That + and * you see there are what JavaScript calls operators.

Here’s where some people might make the mistake of first adding 1 and 2, then multiplying it by 5. Which isn’t how arithmetic works.

The correct way is to first multiply 2 and 5 then add that to 1. This is due to a mathematical concept called **the precedence of operators**. It’s a rule.

There’s plenty of information and charts to help guide you onto what operator takes “precedence” over what. Just understand that * must go before +.

If you want to really control what goes before what and bypass the precedence rule, **you can insert parentheses** like this:

`(1 + 2) * 5`

These parentheses force the addition of 1 and 2 first, then multiplying that by 5 which gives us a totally different result:

`15`

Here’s another note to keep in mind, some operators have equal precedences like multiplication and division. Here, it doesn’t matter which one goes first, the results are the same.

Let’s do a little quiz.

## Arithmetic Quiz

### Example 1

What is the answer to:

`32 + 4 * 3 - 3`

The answer is:

`41`

Because of precedence, it looks more like 32 + (4 * 3) – 3. So it starts with the 4 multiplied by the middle 3. Then, the result of that is added to 32, and then finally 3 is subtracted from the overall.

## What is the remainder or modulo operator?

This one’s special. The **symbol for the remainder or modulo operator is %.**

Its **precedence is equal to * and /**.

It produces the remainder of dividing 2 numbers.

Let’s test this:

## What’s the remainder/modulo for these numbers?

### Example 1

`12 % 3`

The answer is:

`0`

The reason for this being 0, is because once you divide 12 by 3, you are left with nothing else “remaining.”

Let’s take another example, this time with something remaining.

### Example 2

`12 % 5`

The answer is:

`2`

Are you confused yet?

The reason it’s 2 is because that’s what is “remaining” once you remove two 5’s from 12 in the division process. You are left with a “remainder” of 2, not 0.4.

I guess you can think of it as, how many whole integers are left after the division operation?