Help converting string to variable

Hey guys,
I need help with some code.
I need to be able to take user input (for a number) from io.read() and change it from a string into a variable or whatever can be used in math.
e.g

print("please enter a number: ")
number = io.read()
type(number)

when the type(number) executes, it says that the number is a string, how can i change it into a number?

number = tonumber(number)
or directly number = tonumber(io.read())

Okay thanks :P/>/>