Question 839725: On average the United States consumes 3.9 x 10^12 gallons of water each month. If the U.S. population is 3.14 x 10^8 ˏ how many gallons of water is each person in the United States using per month?
I would like to know if I should do (water consumed) divided by (population) {3.9 x 10^12 gal per month divided by 3.14 x 10^8 people} or (population) divided by (water consumed) {3.14 x 10^8 people divided by 3.9 x 10^12 gal per month}. Also if you could show me the answer in scientific notation as well as in standard numerical form as well as how you got there I would be very appreciative.
P.S. the x represents multiplication.
Thank you for your help.
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! united states consumes 3.9 * 10^12 gallons of water each month.
united states population is equal to 3.14 * 10^8.
you want gallons per person so you have to divide the number of gallons of water by the number of people.
this will be equal to:
3.9 * 10^12
------------------------
3.14 * 10^8
3.9 / 3.14 is equal to 1.242038217
10^12 / 10^8 is equal to 10^(12-8) is equal to 10^4
your answer should be:
1.242038217 * 10^4 gallons per person per month.
in standard decimal notation, that's equivalent to 12,420.38217 gallons per person per month.
you can verify by multiplying 1.242038217 * 10^4 by 3.14 * 10^8
that's the number of gallons per month per person multiplied by the number of people.
that number becomes:
1.242038217 * 10^4 * 3.14 * 10^8
1.242038217 * 3.14 = 3.9
10^4 * 10^8 = 10^(4+8) which = 10^12
the answer is 3.9 * 10^12 gallons of water per month which is where we started from so the solution is good.
to find gallons per person, take the number of gallons and divide it by the number of people.
to find persons per gallon, take the number of people and divide it by the number of gallons.
the variable after the "per" is on the bottom.
miles per gallon = miles divided by gallons.
gallons per mile = gallons divided by miles.
that's the general rule of thumb.
scientific notation makes the problem a little more difficult, but follow the rules of scientific notation and you should be able to get the answer.
a reference that might be helpful is:
http://www.purplemath.com/modules/exponent.htm
there are other references on the web.
just do a search on "scientific notation" and a whole bunch will pop up.
some are easier to understand than others.
just look at several until you find one that makes sense to your way of thinking.
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