Effusion/Diffusion Chemistry Help!!!

Question

If 4.83mL of an unknown gas effuses through a hole in a plate in the same time it takes 9.23mL of Argon, Ar, to effuse through the same hole under the same conditions, what is the molecular mass of the unknown gas? (146amu)

Answer 1

Isn't this just standard use of
rate1/rate2 = sqrt(M2/M1)?
I get 146 also.

Answer 2

TY