1. The problem statement, all variables and given/known data The headlights on a car operate typically at 60 W and the parking lights typically at 5 W. Assuming that there are two main headlights and four parking lights, what length of time will it take to discharge a 60 Ah battery, if the lights are left on? 2. Relevant equations I = Q/t V = W/Q P = W/t P = I2*R P = V2/R P = IV 3. The attempt at a solution I have gotten no where with this question. All that I could do was find that the total power consumed by the lights: PT = (2*10) + (4*5) = 140 W , and the charge of the battery: 1 Ah = 3600 C ∴ 60 Ah = 216,000 C , and that's it. I have tried simultaneous equations by substitution and elimination but that doesn't work because all of the equations are derived from the base equations I = Q/t, V = W/Q and P = W/t, so I end up getting P = P all the time. Hint's anybody? Thank you.