Question

When n = energy efficiency and Pin = energy input and Pout = energy output, how can you mathematically represent the correct relationship between the energy you put in something and the energy you get out?

Answer 1

Pout/Pin = n

Answer 2

in general, efficiency = output/input

suppose a process takes 30 J of energy and gives out only 15 J of energy,
then its efficiency = 15/30 = 0.5 or 50%