Excel allows you to do all kinds of calculations and respect mathematical rules.

We will see how to perform simple calculations (addition, subtraction, multiplication, division) and also how to perform operations that use several different operators without making any mistakes 😉

## The = sign

In Excel, all the calculations or formulas start with the = sign. **It's COMPULSORY !!!**

## Add values

To add values in Excel, you just have to write in any cell an operation like this one.

=10+5

In the cell, you see the result and in the formula bar, you see the formula 😉

Take care when you delete the contain of a cell, you could delete a formula and not a value.

## Subtract values

In the same way, to subtract values, you simply write a formula like this

=25-20

But if you write switch the 2 values, the result is not the same

=20-25

## Multiplication and division

Here again, to make a multiplication or division, you just have to write the operation in a cell and you start with **the sign =**

=2*12 =>24

=50/10 =>5

## Let the fun begins

### Order of operations

In math, all the operators don't have the same "power". That's what is called the order of operations.

Multiplication and division **have a stronger rank** than addition and subtraction.

### Wrong example of calculation

What is the result of this calculation **2+3*4 **?

- Many will say the result is 20. If you start from the left, you have
**2+3**, so it's**5**. - And after, you have
**5**(the result of the 2 first values)**times 4**so result**20**

But this solution doesn't respect the order of operations

### Correct solution

In fact, we must **start by the multiplication**.

- So first it's
**3*4=12** - Then, we do
**2+12=14**

And it's the result returns in the cell 😃

### Facebook game

I'm sure you have seen this game in your Facebook timeline and when you look in the answers in comment, are ... WOW 😲😲😲

But if you follow the order of operations, it's easy to find the correct result.

- Row 1: 3 beer bottle = 30.
- A bottle of beer it's 10 =30/3 (ok for every one? 😉)

- Row 2: 1 beer bottle + 2 hamburgers = 20
- We know that a beer bottle = 10
- So 2 hamburgers = 10 (20-10)
- 1 hamburger it's 5 =10/2

- Row 3: (here is the trick) 1 hamburger + 4 pintes = 13
- 1 hamburger = 5
- Here we have 2 group of 2 pintes. So there is 4 pintes
- So, 13-5 (the hamburger) = 8. And 8/4=2.
- The pinte = 2

- Row 4: 1 hamburger + 1 pinte * 1 beer bottle = ?
- So,
**you must respect the prior of the mathematical symbols** - 1 pinte * 1 beer bottle => 2*10 = 20
- 20 + hamburger => 20+5 = 25 😉

- So,

### Use parenthesis

Let's return to our first example **2+3*4**

If you want to calculate the addition before the multiplication it's possible. For that, you must write the addition in parenthesis

=(2+3)*4

This is because, in the order of operations, you have

- The parenthesis
- Multiplication and division
- Addition and subtraction

This point is very important to calculate VAT for instance.

## Calculation with reference

Ok, use Excel with values in the calculation it's easy. But the best, is to re-use the contain of other cells in the formula.

The same rule of order of operations works with values and references

## Percentage increase between 2 values

You can use exactly the same maths operators to calculate the percentage increase between 2 values.

This calculation is one of the most useful in Excel 😉. Have a look at this page for the explanation