A400watt light bulb is left on for 6.5hours. How many kilowatt hour of energy is used?

To find the number of kilowatt-hours (kWh) of energy used by the 400-watt light bulb in 6.5 hours, follow these steps:

Step 1: Convert the power from watts to kilowatts.
1 kilowatt (kW) is equal to 1000 watts (W), so divide 400 watts by 1000:
400 W / 1000 = 0.4 kW

Step 2: Multiply the power in kilowatts by the time in hours.
0.4 kW * 6.5 hours = 2.6 kilowatt-hours (kWh)

Therefore, the 400-watt light bulb, if left on for 6.5 hours, would use 2.6 kilowatt-hours of energy.