Question

When can the reciprocal method be used to calculate total resistance in parallel circuits?

Answer 1

Explicación:

The components are in parallel if they share two nodes.

If there is something between the resistance as in the second image they are no longer in parallel. Taking into account that orange boxes are resistors. First, R3 is added with the resistance that is next to it (series) and the resulting one now will be in parallel with R2.