Is there any international aptitude test for college-level mathematics that can help Graduate Admission? Is there any international aptitude test for college-level mathematics that can help Graduate Admission?
Is there any agency that conduct such a test?
Will it be better to take some courses in Math in the university, apart from my major study program?
 A: Nearly all Ph.D. programs in United States require the GRE Subject Test in Mathematics. This is a standardized test administered by the ETS and measures elementary skill in Calculus (single and multivariable), Linear Algebra, Abstract Algebra, Real Analysis and Topology. The GRE test attempts to measure the effectiveness of your undergraduate classes. If your percentile is high enough, you will stand out.
If, however, you're looking for competitions to pad your resume, consider doing the Putnam Math Competition. This is a challenging 12-problem test administered once a year that requires mathematical knowledge, aptitude and creativity. Scoring well on this test (like Putnam Top 500) demonstrates that you have the potential to tackle challenging problems.
Unfortunately, Putnam competition is U.S. only. You may also be interested in Mathematical Contest in Modeling, which is international. I've heard it referred to as the Putnam Competition of Applied Math. This competition presents three open-ended problems. In a group of {2,3} people, you attempt to answer the problem by developing a mathematical model in the span of several days (around 72 hours, I think)
