Resistance Between Terminals AC and AD

[shimizua]

Homework Statement

What is the resistance between terminals AC? What is the resistance between AD?

An underground telephone cable, consisting of a pair of wires, has suffered a short
somewhere along its length (at point P in the Figure). The telephone cable is L long,
and to determine where the short is, a technician first measures the resistance between
terminals AB to be RAB; then he measures the resistance across the terminals CD to be
RCD.

http://capa-new.colorado.edu/teacher/capalibrary/Graphics/Gtype58/prob08.gif

Homework Equations

So I know that to find resistance we do R=pl/A but I don't really know how I would find it in this situation since it is not like finding AB or CD like I have done before. Please help

The Attempt at a Solution

Not sure if I would just kinda do something like
R(ac)=pL/A ? and just have it be that simple and then
R(ad)=pL/A + R(cd) ? please help

 

[kuruman]

Say x is the distance from A to the short. Can you write an expression for the resistance R_AB in terms of x? How about an expression for R_CD in terms of x?