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 4.00 km long, and in order to determine where the short is, a technician first measures the resistance between terminals AB; then he measures the resistance across the terminals CD. The first measurement yields 15.00 Ω; the second 105.00 Ω. Where is the short? Give your answer as a distance from point C. Assume that the telephone wires are of uniform diameter.
I'm sure which equations to use.
The Attempt at a Solution
I'm not sure how to start on this problem. I know a short circuit is when the resistance is equal to zero, but if it is zero than length ends up being zero due to the linear relationship. I don't get this problem. Please help in any way that you can.