Engineering Basic Circuits - Equivalent Resistance

[subwaybusker]

Homework Statement

Find the Resistance between terminals B-C, B-D

Homework Equations

The Attempt at a Solution

The book says that the 2 80-ohm resistors are in parallel for terminals A-B, and the answer for B-C=90ohms, B-D=85ohms. I don't quite understand why this is. Is it because the 2 80ohm resistors are in series between terminals B-C and B-D, and therefore it short circuits because the other path (wire only) is 0 ohms? Does this mean that whether the resistors are in series or parallel depends on the path taken?

 

[berkeman]

Correct about the short circuit around the 80 Ohm resistors for the path B-C and B-D.