Family of four lives in a three-bedroom house and uses an average of 900 kWh of electricity per month. The family cools their house for three months during the summer with two window-unit air conditioners that each use 350 kWh 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?

Group of answer choices

9,7%

19.4%

38.8%

77.8%

B) 19.4%

Step-by-step explanation:

It is given that average consumption of electricity by the family is 900 kWh per month. Since, there are 12 months in a year, and we have the average consumption of electricity per month, the total consumption for the year would be:

Total electricity consumed in a year = 900 x 12 = 10800 kWh

Next it is stated that during the summer, the same family uses 2 window-unit air conditioners and each of them uses 350 kWh of electricity per month. So, the total electricity used by both units per month would be:

Electricity used by 2 air conditioners in 1 month = 2 x 350 = 750 kWh

Since, the family uses these air conditioners for 3 month, the total consumption for 3 months would be:

Total electricity consumption for 3 months of 2 air conditioners = 3 x 750 = 2250 kWh.

We have to find what percentage of total annual electricity is used to run the 2 air conditioners for three months of summer. So, we have to find 2250 is what percent of 10800. This can be done as:

This means, 2 air conditioners consume 19.4% of the annual electricity.

19.4%

Step-by-step explanation:

Electricity consumption for two air conditioners during summer is 2×350=700 kWh

Consumption of electricity by air conditioners during summer which takes 3 months will be 3*700=2100 kWh

Annual electrical consumption is 900*12=10800 kWh

Percentage of electricity consumed on air conditioners to total annual consumption will be

(2100/10800)×100=19.444444444444444444%

Rounded off, this is 19.4%