Question

note: please make sure to properly format your answers. all dollar figures in the answers need to include the dollar sign and any amount over 1,000 should include the comma ($2,354.67). all percentage values in the answers need to include a percentage sign (%). for all items without specific rounding instructions, round your answers to two decimal places, show both decimal places (5.06). jessicas parents are always telling her to turn off the lights when she leaves her room. the fixture in jessicas room requires four bulbs that each use 75 watts of electricity when theyre on. a. jessicas parents estimate that she leaves the lights on unnecessarily for 2.5 hours per day. how many watt - hours of electricity are used by these bulbs during 2.5 hours? b. approximately how many kilowatt - hours of electricity are used in a year to keep these bulbs lit for 2.5 hours per day? c. at a cost of $0.12 per kilowatt - hour, how much money is wasted per year by keeping these lights on unnecessarily? round to the nearest dollar. d. if five million people keep lights on as jessica does, how much is wasted in unnecessary electric expenses?

Explanation:

Step1: Calculate total watt - power of bulbs

Each bulb is 75 watts and there are 4 bulbs, so the total power $P = 4\times75=300$ watts.

Step2: Calculate watt - hours used in 2.5 hours

Using the formula $W = P\times t$ (where $P$ is power in watts and $t$ is time in hours), we have $W=300\times2.5 = 750$ watt - hours.

Step3: Convert watt - hours to kilowatt - hours

Since 1 kilowatt - hour = 1000 watt - hours, the number of kilowatt - hours $k=\frac{750}{1000}=0.75$ kilowatt - hours per day.

Step4: Calculate kilowatt - hours used in a year

There are 365 days in a year, so the total kilowatt - hours in a year $K = 0.75\times365=273.75$ kilowatt - hours.

Step5: Calculate money wasted per year

The cost is $0.12$ per kilowatt - hour, so the money wasted per year $M=273.75\times0.12 = 32.85\approx33$ dollars.

Step6: Calculate wasted cost for five million people

If there are 5000000 people, the total wasted cost $T = 33\times5000000=165000000$ dollars.

Answer:

a. 750 watt - hours
b. 273.75 kilowatt - hours
c. $\$33$
d. $\$165000000$