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Homework Help: Carbon Dioxide Output Percentage Change

  1. Nov 4, 2013 #1
    1. The problem statement, all variables and given/known data
    Question: If petroleum used in transportation were replaced by electricity generated by coal, what would be the percentage change in carbon dioxide output?

    Refer to the following diagrams for values:

    Given Information:
    • Petroleum has an efficiency rating of 1/4 in transportation.
    • Coal that is burned to produce electricity has 1/3 efficiency.
    • Petroleum has 2/3 the carbon footprint of coal.
    • Switching to coal means: using less of a fuel; fuel has higher carbon footprint.

    2. Relevant equations
    [itex]Percentage \ change = \frac{Initial - Final}{|Initial|}[/itex]

    3. The attempt at a solution
    [itex]Percentage \ change = \frac{1170 - 1180}{|1170|} \\[/itex]
    [itex]Percentage \ change = -0.56\%[/itex]
  2. jcsd
  3. Nov 5, 2013 #2


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    Science Advisor
    Homework Helper
    Gold Member

    I don't know which numbers you fished out of those table to arrive at 1170 and 1180, but you do not need those tables at all for this question.
    Suppose you need X units of transport energy. How many units of petrol would you need for that? What would be the number of CO2 units produced? Do the same calculation for coal.
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