Question

A 100-W light bulb is plugged into a standard 120 V outlet. How much does it cost per month (31 days) to leave the light turned on?

Answer 1

Answer:

4.836 dollars

Explanation:

When the power in watts is multiplied by the amount of time the power is used we get the power in the following form.

The power in kWh is

$P=100\times 31\times 24\times 10^{-3}\\\Rightarrow P=74.4\ kWh$

Cost of kWh = 6.5 cents (assumed)

Cost in a month is given by

$74.4\times 6.5=483.6\ Cents=\dfrac{483.6}{100}=4.836$

The cost per month is 4.836 dollars per 31 days