Question

Medal
The energy information administration reports that if every U.S. household switched 4 h of lighting per day from incandescent bulbs to compact fluorescent bulbs, we would save 31.7 billion kilowatt hours of electricity a year , or 33% of the total electricity used for home lighting. What is the total electricity used for home lighting in this country? round to the nearest tenth of a billion.

Answer 1

So the compact fluorescent bulbs save 77% of the energy am I correct? I'm confused with the question...

Answer 2

yes

Answer 3

So 31.7 billion is the 33%. You have to find the 100%

Answer 4

yes

Answer 5

From that I immediately see that you could simply multiply by 3, but it will give you 99%, to prevent that you can use the rule of three, I don't know if you ever heard of it.

31.7 --- 33%
x --- 100%

This basically is if 31.7 is 33%, then 100%..... It's the same as 31.7 / x = 33/100
You just cross multiply that. 31.7(100) will be 3170 and divide by 33.
x=96.060606....
Rounded to the nearest tenth will be 96.1 bilion kilowatt hours.

I'm sorry if I confused you with the rule of three but I think it's the easiest and fastest way to do it.

Answer 6

so the answer is 96.060606 rounded to the nearest billion?

Answer 7

The rule of three is basically the same thing as cross-multiplication.... It's just rationalized a different way.

Answer 8

Yes, rounded will be 96.1 bilion kilowatt hours

Answer 9

thank you soo much :)