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Unit conversion problem 
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#1
Jan1013, 01:09 PM

P: 162

1. The problem statement, all variables and given/known data
If one truck runs on 6000 barrels of oil per year, how many trucks could run on the oil produced in the US in one year (1.9*10^10 barrels)? 2. Relevant equations (6000 barrels/year) used by one truck (1.9*10^10 barrels/year) for US production 3. The attempt at a solution I simply divided 1.9*10^10 by 6000 to get 3,000,000. I'm confused about the fact that 3,000,000 is not in units of "trucks". How can I set up this problem properly to include trucks as my units? 


#2
Jan1013, 01:16 PM

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P: 5,196

Hello cytochrome,
[tex]\left(\frac{1.9 \times 10^{10}~\textrm{barrels}}{1~\textrm{year}}\right) \cdot \left(\frac{1~\textrm{truck}}{6000~\textrm{barrels}}\right)[/tex] The unit of barrels cancels, leaving trucks and years, so your result is in trucks/year ("trucks per year"). EDIT: ACTUALLY, you can consider the quantity of 6000 to have units of "barrels per truck, per year" which would be barrels/(trucks*years). So, in that case, there would be 1 year in the numerator of the righthand factor in parentheses, and the year unit would cancel as well, leaving only trucks. However, the way I did it is fine too. In this case, the way to think about it is that a "truck" is a unit of volume equal to the amount of oil needed to run one truck for a year. So, what your unit conversion is doing is saying that the US produces 3,000,000 "trucks" worth of oil per year. It's just a matter of interpretation. 


#3
Jan1013, 05:06 PM

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P: 5,067

Another version:
6000 bbl per year per truck 1.9 x 10^{10} bbl per year 


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