Final answer:
Without specific information about the charge distribution, it is not possible to determine the charge enclosed by spheres of radii 5, 10, and 20 cm. The provided formula suggests a charged relationship, but without context, it does not directly answer the student's question.
Step-by-step explanation:
The question asks about the charge enclosed by spheres of different radii. To determine the charge enclosed, we need to consider the situation presented in the information provided, which might relate to electrostatic concepts such as electric charges, electric fields, or Gauss's Law.
The reference information describes various scenarios involving charged spheres and spherical conductors. However, it does not provide direct answers to the charge within spheres of radii 5, 10, and 20 cm without additional context or information about the charge distribution. Nevertheless, the extracted formula 91 92 = ±√√/5.6 × 10^-18 C^2 = ±2.4 nC implies a relationship that could be used in a specific context to solve for charge values.
If we assume that all of the spheres mentioned have the same charge distribution as in the examples, then we could postulate that the charge enclosed by the spheres is ±2.4 nC (nanocoulombs). But without knowing the exact conditions, such as whether these charges are uniformly distributed in volume or on the surface, or whether they are point charges at the centers, we cannot provide a definitive answer.