Question

A family of four lives in a three-bedroom house and uses an average of 900kWh of electricity per month. The family cools their house for three months during the summer with two window-unit air conditioners that each use 350kWh of electricity per month. Which of the following is the percentage of the family's total annual electricity that is used to run the two air conditioners for the three summer months?

1) 9.7
2) 19.4
3) 38.8
4) 77.8

Answer 1

The two air conditioners use 2,100 kWh during the summer months, which is 19.4% of the family's total annual electricity usage of 10,800 kWh.

Step-by-step explanation:

To determine the percentage of the family's total annual electricity usage that is used by the two air conditioners during the summer, we need to calculate the total electricity usage for the air conditioners and compare it to the annual usage.

The family uses 900 kWh monthly, which is 900 kWh x 12 months = 10,800 kWh annually. During the summer months, the two air conditioners use 350 kWh each per month. Since there are two air conditioners, their combined consumption is 350 kWh x 2 = 700 kWh per month. For three months, they use a total of 700 kWh x 3 months = 2,100 kWh.

To find the percentage of the annual usage that 2,100 kWh represents, we use the formula:

Percentage of annual electricity used by air conditioners = (Electricity used by air conditioners / Total annual electricity usage) x 100

So, the calculation is (2,100 kWh / 10,800 kWh) x 100 ≈ 19.4%.

Therefore, the answer is option 2) 19.4%.