The math needed in top 20 schools in management is equivalent to that of a bachelor degree in math. If not, you should at least have three semesters of calculus, and a course in differential equations, probability, and linear algebra. The more the merrier. Finance needs more math than the other two.
"那是因为自由以前没好好重视数学,如果将来重视它,多用心再它上面,我相信没什么大问题。"
-- only if you can convince the admission committee : )