Carlota does 2000 cap j of work on a machine. The machine does 500 cap j of work. What is the efficiency of the machine?

Efficiency is useful work output divided by work input, multiplied by 100%. The machine receives 2,000 J of work and does 500 J of work, so its efficiency is (500 ÷ 2,000) × 100% = 25%. The correct choice is 25 percent.

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