You are about to invest in a 66-inch flat screen tv. these tvs come in both energy star and non-energy star models. the cost of electricity is $0.15 per kilowatt-hour, and you expect to watch tv an average of 4 hours per day.

the non-energy star model uses 0.5 kw (half a kilowatt). how much will it cost you per year for electricity to run this model?

if the energy star model uses only 40 percent of the amount of electricity used by the non-energy star model, how much money would you save on your electric bill over 5 years by buying the efficient model?

We want to compare the energy consumption of two TVs, we will see that after 5 years, using the energy-efficient tv will save you a total of $328.5

The given information is:

So, using this tv, in one day you spend:

$0.15*0.5*4 = $0.30

In a year there are 365 days, so you will spend a total of:

365*$0.30 = $109.5

The other model uses 40% of the amount of energy, so it uses:

0.4*0.5 kW per hour = 0.2 kW per hour.

So the cost per day is:

$0.15*0.2*4 = $0.12

in one year, the cost will be:

$0.12*365 = $43.8

Now we want to see how much you will save after 5 years, then we just need to find 5 times the difference between the cost per year of each TV, we will get:

5*($109.5 - $43.8) = $328.5

This means that using the energy star model, you would save $328.5 after 5 years.

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When the diameter is doubled, the circumference is doubled.

Step-by-step explanation:

Let diameter = 2

d=2=2r

∴r=1

Circumference = 2πr=2π(1)=2π

Let diameter = 4 (double)

d=4=2r

∴r=2

Circumference = 2πr=2π(2)=4π

We can see that when the diameter is doubled, the circumference is doubled.