Efficiency is useful output divided by total input, using either energy or power. A decimal efficiency can be multiplied by 100 to express it as a percentage. Reducing unwanted transfers, for example with lubrication, can increase efficiency; it cannot exceed 100%. Example: A machine has 0.75 efficiency and receives 400 J. Calculate useful output and dissipated energy. Useful = 0.75 × 400 = 300 J; dissipated = 400 − 300 = 100 J. Use clear labels. Check your reasoning. Distinguish the quantities.