There is no need to provide a get & set function for every private member variable. Try to provide only the public functions that are necessary - in this case it is the generateNumber function. It sets the number variable and returns it, so the get & set functions aren't needed.
If you had a get & set for each private member variable, then you might as well make them all public !!!
Now you just need a switch statement to decide what the prize is.
Yes. Essentially all these two functions do is assign the value of the argument to the member. Its good practice because if in the future you want to change the member variables or add more functionality, you don't need to re-write all the other code: The class interface stays the same so that any other programmers using your class don't have to worry about changing anything.