Problem 2.14   Source:   Problem elaborated by the author of the site.

Calculate the equivalent resistance between the B-E points by considering the shorted D-E points, as shown in Figure 02-14.1

Solution of the Problem 2.14

Note that if the D-E points are short-circuited, this means that the resistors between these two points may be disregarded. So we need to calculate the equivalent resistance only between the B-D points.

Thus, between the points B-C (down the path) we have two resistors in series totaling 20 + 10 = 30 Ω. And by the way B-A-C we have three resistors in series, which together add up to 30 + 50 + 40 = 120 Ω. Therefore, solving the parallel of these two sets we find:

So to finish, we need to add the resistor value between the C-D points, whose value is 20 Ω. So: