The global warming potential (GWP) of a greenhouse gas is measured in

Question

The global warming potential (GWP) of a greenhouse gas is measured in teragrams (or million metric tons) of carbon dioxide (CO2) equivalent (Tg CO, Eq.). In 2010, total U.S. greenhouse gas emissions were 6821.8 Tg CO, Eq. The primary greenhouse gas emitted by human activities in the United States was CO2, representing approximately 83.6% of total greenhouse gas emissions. Overall, from 1990 to 2010, total emissions of CO2, increased by 605.9 Tg CO2, Eq. (11.90%). The largest source of CO2, and of overall greenhouse gas emissions, was fossil fuel combustion.

Within the United States, fossil fuel combustion accounted for 94.4% of CO2, emissions in 2010. Globally, approximately 30,313 Tg of CO2 were added to the atmosphere through the combustion of fossil fuels in 2010, of which the United States accounted for about 18%.

CO2, emissions result both directly from the combustion of fossil fuels for use in one of four end-use sectors (Transportation, Industrial, Residential, and Commercial)—and indirectly from the generation of electricity that is consumed by these sectors.

Sajjad1994 · Answer

Official Explanation

Statement: In 2010, total U.S. CO2 emissions were approximately 5707.4 Tg.

In 2010, fossil fuel combustion accounted for 94.4% of CO2 emissions in the United States (Tab 1), and total CO2 emissions from fossil fuel combustion were 5387.8 Tg (Tab 2). Thus, if x were the total CO2 emissions, then:

5387.8=94.4%x

x=\frac{5387.8}{94.4} 100

x=5707.4

Answer: Yes

Statement: In 2010, U.S. greenhouse gas emissions, not counting CO2 emissions from fossil fuel combustion for electricity generation, were 4563.3 Tg CO2 Eq.

In 2010, total U.S. greenhouse gas emissions were 6,821.8 Tg CO2 Eq. (Tab 1). Total CO2 emissions from fossil fuel combustion for electricity generation equaled the sum of CO2 emissions from fossil fuel combustion for electricity generation for each of the four end-use sectors. This sum is:

(4.5+637.6+843.5+772.9) Tg CO2 Eq. 2258.5 Tg CO1 Eq.

The difference between 6821.8 and 2258.5 is 4563.3, which is the number of Tg CO2 Eq. of U.S. greenhouse gas emissions, not counting CO2 emissions from fossil fuel combustion for electricity generation.

Answer: Yes

Statement: In 2010, methane emissions in the U.S. were less than 6% of total U.S. greenhouse gas emissions.

From Tab 1 you know that fossil fuel combustion accounted for 94.4% of CO2 emissions in 2010, and that CO2 represented approximately 83.6% of total greenhouse gas emissions. Therefore, CO2 emissions from fossil fuel combustion accounted for 83.6% times 94.4% of total greenhouse gas emissions in the United States. That figure is 78.9%.

Answer: No

Sajjad1994 · Answer

Official Explanation

Statement: U.S. Transportation sector

From Tab 1 you know that “globally, approximately 30,313 Tg of CO2 were added to the atmosphere through the combustion of fossil fuels in 2010.” Tab 2 gives you the figures for the CO2 emissions from fossil fuel combustion by each enduse sector. Transportation emitted 1750.0 Tg of CO2. If this number is x percent of 30,313, then:

1750=x%(30,313)

x=\frac{1750}{30,313} 100

x=5.77

In other words, the U.S. Transportation sector emitted approximately 5.77% of the world’s CO2 emissions through the combustion of fossil fuels in 2010.

Answer: Yes

Statement: U.S. Transportation sector

Follow the same process as in Question 9.1, and you’ll find that the 1183.7 Tg of CO2 that the U.S. Residential sector emitted in 2010 was 3.90% of the world’s CO2 emissions through the combustion of fossil fuels in 2010.

Answer: No

Statement: U.S. Commercial sector

Follow the same process as in Question 9.1, and you’ll find that the 997.1 Tg of CO2 that the U.S. Commercial sector emitted in 2010 was 3.29% of the world’s CO2 emissions through the combustion of fossil fuels in 2010.

Answer: No

Sajjad1994 · Answer

Official Explanation

3. In 2010, CO2 emissions from fossil fuel combustion in the United States accounted for what percent of total greenhouse gas emissions in the United States?

Explanation

From Tab 1 you know that fossil fuel combustion accounted for 94.4% of CO2 emissions in 2010, and that CO2 represented approximately 83.6% of total greenhouse gas emissions. Therefore, CO2 emissions from fossil fuel combustion accounted for 83.6% times 94.4% of total greenhouse gas emissions in the United States. That figure is 78.9%.

Answer: B

Gemmie · Answer

1. For each of the following statements, select Yes if it can be reasonably inferred from the given information. Otherwise, select No.

In 2010, total U.S. CO2 emissions were approximately 5707.4 Tg. => Yes

Tab 2: Total CO2 emisssions from fossil fuel of US in 2010 is 5387.8
Tab 1: Within the United States, fossil fuel combustion accounted for 94.4% of CO2, emissions in 2010

=> Total US CO2 emissions:  5387.8 \div 0.944 = 5707.4

In 2010, U.S. greenhouse gas emissions, not counting CO2 emissions from fossil fuel combustion for electricity generation, were 4563.3 Tg CO2 Eq. => Yes

Tab 1: Total greenhouse gas emissions: 6821.8
Tab 2: Total US CO2 emisssions from fossil fuel for electricity generation in 2010 is
 
 Transportation: 4.5 
 Industrial: 637.6 
 Residential: 843.5 
 Commercial: 772.9 
 ==> Total: 2258.5  
==> U.S. greenhouse gas emissions, not counting CO2 emissions from fossil fuel combustion for electricity generation: 6821.8 - 2258.5 = 4563.3

In 2010, methane emissions in the U.S. were less than 6% of total U.S. greenhouse gas emissions. => No

Tab 1:
 
 The primary greenhouse gas emitted by human activities in the United States was CO2, representing approximately 83.6% of total greenhouse gas emissions 
 We do not know the composition of the remaining 17.4% greenhouse gas emission and therefore do not know whether methan emissions were more or less than 6%

2. For each of the following sectors, select > 5.00% if the sector accounted for more than 5.00% of the world’s CO2 emissions in 2010. Otherwise, select < 5.00%.

World CO2 emissions in 2010: 30,313

U.S. Transportation sector:  \frac{1750}{30,313}  = 0.0577 = 5.77% > 5%

U.S. Residential sector:
 
 1183.7 much less than 1750 (Transportation) (only around 2/3). 
 Meanwhile, Transportation is just slightly more than 5% 
 Residential must be less than 5%  
U.S. Commercial sector: Similarly, must also be less than 5%

3, In 2010, CO2 emissions from fossil fuel combustion in the United States accounted for what percent of total greenhouse gas emissions in the United States?

Tab 2: CO2 emissions from fossil fuel combustion in the United States in 2010: 5387.8
Tab 1: Total greenhouse gas emissions in the United States in 2010: 6821.8

% =  \frac{5387.8}{6821.8}  = 78.9%

placeatex · Answer

For the first part of question 1, I used the information in the first tab that reads:

"In 2010, total U.S. greenhouse gas emissions were 6821.8 Tg CO, Eq. The primary greenhouse gas emitted by human activities in the United States was CO2, representing approximately 83.6% of total greenhouse gas emissions."

Since 83.6% of 6821.8 is ~5703, I went with 'No'. Can someone explain why this is incorrect? Have I interpreted the information incorrectly, or should I have considered 5703 to be roughly equal to 5707?

egmat · Answer

Hi placeatex,

Good news: your interpretation isn't wrong at all. You used a perfectly valid path, and your number actually  confirms  the statement rather than contradicting it.

Here's what happened. You worked from  Tab 1 : total GHG =  6821.8 , and CO2 = ~ 83.6%  of that, giving  0.836  x  6821.8  ≈  5703 . The official path instead uses  Tab 1 + Tab 2 : fossil-fuel CO2 =  5387.8  is  94.4%  of all CO2, so total CO2 =  5387.8  ÷  0.944  ≈  5707.4 .

Two roads, two numbers - but look at how close they are:  5703  vs  5707.4 , a gap of about  4  out of  5700 , or  less than 0.1% .

Why the tiny gap?

Your route leans on the figure " approximately83.6% ." That percentage is itself rounded, so multiplying by it carries a small rounding error. The fossil-fuel route ( 94.4%  of an exact table value) is a bit more direct, so it lands on  5707.4 . Neither is "the true" number - both are estimates of the same quantity.

Why the answer is Yes.

The statement asks whether total CO2 was " approximately5707.4 ." That word  approximately  is the key. Your  5703  and the official  5707.4  are effectively the same figure - both say total CO2 was about  5700  Tg. So the statement  can be reasonably inferred , and the answer is  Yes .

So the fix isn't in your math - it's in reading "approximately" as allowing that small rounding difference, instead of demanding an exact  5707.4 . Whenever a statement says  approximately , treat two estimates within a fraction of a percent as a match.

Answer: Yes, Yes, No

The global warming potential (GWP) of a greenhouse gas is measured in

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> 5.00%	< 5.00%
		U.S. Transportation sector
		U.S. Residential sector
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GMAT Multi-Source Reasoning (MSR) Questions

The global warming potential (GWP) of a greenhouse gas is measured in

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