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

Efficiency is useful energy output divided by total energy input. Since 36 kWh is 75% of the input, the input is 36 ÷ 0.75 = 48 kWh. The energy lost is 48 − 36 = 12 kWh, so the correct choice is 12 kWh.

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