The energy output of a fan is 36 kWh. The fan is 75% efficient. How much energy is lost to the surroundings?

A) 12 kWh

B) 36 kWh

C) 48 kWh

D) 84 kWh

I would say the answer is A. 12 kWh because:

If the fan is 75% efficient, and the output was 36 kWh, divide the 36 by 3, which gives you 12. So originally, the total energy was 48 kWh, but 12 kWh was lost (25%), which leaves the 36 kWh (75%) as the output.