A new LED light bulb uses 10 watts of power. Since energy = power × time , then the energy used for this light bulb can be found my multiplying the power times the time the bulb is lit. If the bulb is lit for one hour, the energy used will be 10 watt*hours or 10 Wh. If three 10 watt bulbs in one room are kept on for 5 hours, how many watt*hours of energy are used?