A uniform wire is cut into 4 segments. Each segment is twice as long as the earlier segment. If the shortest segment has a resistance of 4 ohm, find the resistance of original wire.

The resistance of a piece of wire is directly proportional to its length, so we know that just like the length, the resistance of each segment is also twice the resistance

of the previous ('earlier') segment.

So the resistances of the segments are:

4

8

16

32

and their total resistance before they were cut up was

(4 + 8 + 16 + 32) = 60 ohms