A 40 cap w bulb is left on from 9:00 p.m. to 6:30 a.m. How much energy was used by the bulb?

The bulb is on for 9.5 hours, from 9:00 p.m. to 6:30 a.m. A 40-watt bulb uses 0.04 kilowatts, so its energy use is 0.04 × 9.5 = 0.38 kWh. The correct choice is 0.38 kWh.

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