Seriously though, don't worry about that ratio, it's just an estimate. Yes, in the engineering faculty you'll probably notice much more guys than girls. But the guy:girl ratio also depends on which stream you're doing. In some streams such as mechanical, guys far out number the girls whereas in software engineering and especially civil, it's a more even split.
In most streams of engineering, two first year maths subjects are compulsory. There are plenty of girls in those.