Alec Meyer6,301 Points
Not sure why this isn't correct.
int x = 4; int y = 6; return (double) x / y; /* 0.6666666666666663 */
That sure looks like a floating point number to me.
Steven Parker173,904 Points
Assuming the comment was not part of your answer, I think the challenge doesn't like the space between the cast and the variable name. Try it without and I'll bet it gets judged as correct.
Since this isn't a syntax restriction, you might want to submit a bug report to the Support folks.