 # Issues with the mathematic operations

Hey there, I’m trying to do a food app in which I try to multiply three input user data among them and with other double numbers. Any clue?

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@markk

If you are using a combination of Integer inputs and Floating point inputs where you are multiplying them together, then you need to convert them to the same type, preferably Double if one of them is a decimal quantity.

So let’s say you have a recipe which lists the quantities for a single serve and you want to get the quantities of each for a number of people.

For example:

``````let cupsOfMilk = 1.5  //  Xcode will infer as a Double

let people = 5  // Xcode will infer as an Integer

let totalCupsOfMilk = cupsOfMilk * Double(people)

print(totalCupsOfMilk)
``````

Thanks, but the thing is I need to multiply the user input and not an specific number. Sorry maybe it’s to obvious but I’m quite new in programming.

This is:

You need to convert the user’s input, which is a `String` into an `Int` or `Double` or some other type

And then do the math

What are `Pes`, `Altura`, and `Edat`?? Based on the error they look like the name of `UITextField`s

And how can I do that?

Yes exactly are three different UITextFields which I need to multiply and with other numbers such as 9.99 and 5.75.

First you need the value from the text field, I’ll use `Pes` for this example, but they will all be the same, also btw I would rename this to `pesTexField`, variables shouldn’t start with uppercase letters, and naming it text field helps you know that it’s a `UITextField`

``````let stringAmount = pesTextField.text // this is a string, because the .text property, returns the string of what’s typed in the text field

let doubleAmount = Double(stringAmount) // this is now a double, as long as the user typed something valid, ie doesn’t type “five” but a real number

let multiplier = Double(5) // just a random number I thought of

let value = doubleAmount * multiplier
``````

You could put this code in a function after a button is clicked