The electrical resistance of a wire varies as its length and inversely as the square of the diameter. R = (k*L)/(d^2) where k = proportionality constant Since the two wires have the same material, their proportionality constant is same. Equating that (R1*d1^2)/L1 = (R2*d2^2)/L2
Given that R1 = 10 ohms, d1 = 1.2 mm or 0.0012 m, L1 = 18 m, d2 = 1.5 mm or 0.0015 m, L2 = 27 m, and R2 is unknown. Therefore [10*(0.0012^2)]/18 = [R2*(0.0015^2)]/27 R2 = 9.6 ohms
The cost on startup is $10 and each painted rock cost around $0.75 to make. A store pays startup cost and buy painted rocks for $0.75 each there no profit because the cost price and selling price is the same.
