How much energy in kWh does a 100 W bulb use in 5 hours?

Q. How much energy in kWh does a 100 W bulb use in 5 hours?
Answer: 0.5 kWh
Notes: Energy (kWh) = Power (kW) × Time (hr); 100 W = 0.1 kW; 0.1 × 5 = 0.5 kWh.

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