I know we get a lot of these here, and the general consensus is that stellar performance in one major (Physics), is better than average performance in two majors. However this question isn't exactly in regards to graduate school admissions. It's more of a question is regards to the usefulness of a secondary degree which may supplement a Physics degree. The secondary degree in question, is called "Mathematics/Statistics (Composite"). It's an "applied mathematics" degree geared toward the sciences. If one was to leave the performance aspect out of it, and assume that someone got great grades in both degrees, how useful would this secondary degree be in the field of Physics? Here's a listing of some of the courses. These are the REQUIRED classes, but 15 additional required credits are spent on electives. 6 from Math, and 9 from Statistics. Calculus I Calculus II Calculus III (Multivariable) Linear Algebra ODE Foundations of Analysis Intro to Algebraic Structures Introduction to Analysis Introduction to Probability Introduction to Mathematical Statistics Statistics for Scientists Linear Regression and Time Series Design of Experiments As you can see, many of these are already required for the Physics degree. From a strictly useful standpoint, how much would one benefit from these additional classes in the field of Physics? Keep in mind there are a lot of options for electives such as Topology, Differential Geometry, PDEs, etc. With only a Physics degree, the only math classes that would be seen would be Calc 1-3, LA, ODE.