How to get numbers after comma in F#

Question

I want to get 4 numbers after comma in F# : This is my code :

// Learn more about F# at http://fsharp.org
// See the 'F# Tutorial' project for more help.

open System

[<EntryPoint>]
let main argv = 

    let num = Console.ReadLine() |> float
    Console.WriteLine(num)

    Console.Read() |>ignore
    0

Answer 1

And this's result :

open System

[<EntryPoint>]
let main argv = 

    let num = Math.Round(Console.ReadLine() |> float, 3) 
    Console.WriteLine(num)

    Console.Read() |>ignore
    0