A machine takes in 500 J of energy and gives out 375 J of useful work. What is its efficiency?
Answer and explanation
Correct answer: D. 75%
- Step 1: Efficiency = useful output ÷ input × 100. Step 2. 375 ÷ 500 × 100 = 75%. Answer: 75%. Why not the others: 25% is what you get if you give the wasted fraction. 125% is what you get if you give the wasted energy as a percentage. 95% is what you get if you round the answer up.
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