why here a int and not a float ?

 Hello,



I try to learn Ocaml by following the Ocaml from the very beginning.



I have to write a function that multiplies a number by 10.



So I did :  let multiply_ten x = x * 10 ;;



but to my surprise I see that the function has this : 
val multiply_ten : int -> int = <fun>



How can I change it so I can also calculate 2.5 * 10 ?



Roelof