1. The problem statement, all variables and given/known data A lift motor is 70% efficient. It dose 450 000j of work lifting a load to the top floor of a building. 2. Relevant equations What electrical energy input is required to do this? 3. The attempt at a solution I first did output/input * 100 I transposed the formulae so I did 450 000* 0.7 which gave the wrong answer. When I looked at the answer is say this is the correct way is 450 000 * 100/70 Am I right in saying that when you do it this you are calculating what it is at 100% efficiency and then calculating the difference?