A120 watt light bulb uses about 0.1 kilowatt of electricity per hour. if electricity costs $0.20 per kilowatt hour how much does it cost to have a bulb on for an hour?

$0.02 is the cost to have the bulb on for an hour

Step-by-step explanation:

A 120 watt light bulb uses about 0.1 kilowatt of electricity per hour

We can assume 1 kilowatt per hour = 1 unit

So total units of electricity consumed in 1 hour = 0.1 × 1

= 0.1 kilowatt hour or 0.1 unit

Since cost of one unit or 1 kilowatt hour is = $0.20 per unit or kilowatt hour.

Therefore, total cost to have this bulb on for an hour = Number of units consumed by the light bulb × per unit cost

= 0.1×0.20

= $0.02

$0.02 is the cost to have the bulb on for an hour.