Nucleus: Practice Problem & Solution

Solution Explained:

To solve this problem, we apply the core principles of Nucleus. Understanding the underlying formula is key to arriving at the correct answer below:

The radius of a nucleus is related to its mass number by $R = R_0 A^{1/3}$. The ratio of their radii is $R_1 / R_2 = (A_1 / A_2)^{1/3} = (125 / 64)^{1/3}$. This gives $R_1 / R_2 = 5 / 4$, so the ratio is $5 : 4$.