A furnace releases 3500 kJ of energy, with 900 kJ useful. What is the efficiency?

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Multiple Choice

A furnace releases 3500 kJ of energy, with 900 kJ useful. What is the efficiency?

Efficiency is a measure of how much of the input energy is turned into useful energy. It is calculated by dividing the useful energy by the total energy supplied and multiplying by 100 to get a percentage. Here, 900 kJ is useful and 3500 kJ is the total energy supplied, so the efficiency is 900 ÷ 3500 × 100 = 25.7%. This means about a quarter of the energy does useful work, while the remaining energy is lost as heat or other losses. The numbers given fit this ratio, so 25.7% is the correct efficiency.

Efficiency is a measure of how much of the input energy is turned into useful energy. It is calculated by dividing the useful energy by the total energy supplied and multiplying by 100 to get a percentage. Here, 900 kJ is useful and 3500 kJ is the total energy supplied, so the efficiency is 900 ÷ 3500 × 100 = 25.7%. This means about a quarter of the energy does useful work, while the remaining energy is lost as heat or other losses. The numbers given fit this ratio, so 25.7% is the correct efficiency.

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