Let’s take one **classic calculator** And **the app** from the **iPhone calculator** and we perform on both **same operations.** If we are dealing with two additions/subtractions in a row, the result of the two devices will be the same. But if we perform for example a sum followed by a multiplication (or division), the two **results** they will be **different**. But **how is it possible?** Let’s see it together in this article.

## The classic calculator cannot distinguish operations

Let’s place a classic calculator and an iPhone side by side and perform the same operations on both, one after the other:

30 + 20 / 2

On the two screens we will see two different results appear: **25** on the calculator, **40** on the iPhone.

But how is this possible? And which of the two results is correct?

Formally, the **correct result is that of the iPhone**but the **calculator** he didn’t “miscalculate”, he simply **performed a different operation**.

### The order of operations

One of the first things we learn in school is that mathematical operations have a precise order.

If several operations coexist, such as addition and division in this case, and there are no parentheses, they have the **precedence multiplication** And **division** on addition and subtraction. The correct result of the equation *30+20/2 *in this case it is therefore *40*since the division must be performed first and then the addition, from which *30+10=40.*

**How come** then the calculator gives us as a result * 25?*Simply put, classic calculators are not programmed to do multiple operations at the same time, so they

**perform one by one**

**in order of appearance**. In this case, then, the calculator is performing

**(30+20)/2=25**.**The phone app, on the other hand, can do something more.**

After we type a sum, before saying the result it waits to see what operation we will do next: if it is another sum, then it gives us the partial result, if instead it is a multiplication it waits to know what we will multiply by and first does the multiplication, then the sum.