If r = KL/d2 find L to the nearest tenth foot if r = 2.5 ohms, k = 10.8 and = 85 mil

The electrical resistance r of a wire varies directly proportional to its length L and inversely as the square of its diameter d:

r = K * L / d^2

Looking for L, we rearrange the equation:

L = r * d^2 / K

L = 2.5 * (85) ^2 / 10.8

L = 1672.45 mil

1 foot is equivalent to 12,000 mil, therefore converting the unit:

L = 1672.45 mil * (1 foot / 12000 mil)

L = 0.14 foot = 0.1 foot