The resistance R of a wire varies directly as its length L and inversely as the square of its diameter d. (a) Write an equation that expresses this joint variation. (Use k for the constant of proportionality.) R = KL 2 (b) Find the constant of proportionality if a wire 1.2 m long and 0.005 m in diameter has a resistance of 160 ohms. (Round your answer to six decimal places.) k = (c) Find the resistance of a wire made of the same material that is 3 m long and has a diameter of 0.009 m. (Round your answer to the nearest whole number.) X ohms R = (d) If the diameter is doubled and the length is tripled, by what factor is the resistance changed? 3/4