I'm a female applying to business school this time around, but I have a different take on it. My undergraduate degree is in Management Information Systems, which is a majority male degree, so I'm very used to my classes being majority male. My workplace is majority male as well, though my particular group in it is fairly evenly mixed. I very rarely find majority male groups intimidating.
There's a more heartening way to look at the gender/skill disparity: in an MBA program you will likely be split up into sections and then into small working groups. You'll probably have at least one guy or girl in your group that is stellar at math. So even if you feel a little insecure about your math skills (or you legitimately are not as good at math), you can utilize their skills to double check your work. Learn all you can from them. It's also likely you'll be stronger in a different area (for me, it's communication skills), that you can "trade", so to speak, to add value to the group. Trust me, that math-heavy person that might not be so great at communicating the conclusions he or she comes to will love you helping the group turn it into a great presentation or paper. Quantitative skills are not the only useful skills by a long shot.