The combustion of one gallon of automobile fuel produces about 5 pounds of carbon (in CO₂). Two autos are making a trip of 600 miles. The first auto gets 20 miles per gallon, and the second gets 30 miles per gallon. Approximately how much less carbon (in CO₂) will be produced by the second auto on this trip?

We have been given that the combustion of one gallon of automobile fuel produces about 5 pounds of carbon (in CO₂). Two autos are making a trip of 600 miles.

Let us find amount of fuel used by autos by dividing the total distance by their mileage.

[tex]\text{Fuel used by 1st auto}=\frac{\text{ 600 miles}}{\frac{\text{ 20 miles}}{\text{gallon}}}[/tex]

[tex]\text{Fuel used by 1st auto}=\frac{\text{ 600 miles}}{\text{ 20 miles}}\times \text{gallon}[/tex]

[tex]\text{Fuel used by 1st auto}=30 \text{ gallons}[/tex]

[tex]\text{Fuel used by 2nd auto}=\frac{\text{ 600 miles}}{\frac{\text{ 30 miles}}{\text{gallon}}}[/tex]

[tex]\text{Fuel used by 2nd auto}=\frac{\text{ 600 miles}}{\text{ 30 miles}}\times \text{gallon}[/tex]

[tex]\text{Fuel used by 2nd auto}=20 \text{ gallons}[/tex]

Let us find the difference of fuel used by both autos.

[tex]\text{Number of gallons that 2nd auto used less than 1st auto}=30-20[/tex]

[tex]\text{Number of gallons that 2nd auto used less than 1st auto}=10[/tex]

Since one gallon of automobile fuel produces about 5 pounds of carbon, so 10 gallons of fuel will produces [tex]5\times 10=50[/tex] pounds of carbon.

Since 2nd auto used 10 gallons less than 1st auto, therefore, 2nd auto will produce 50 pounds less carbon than 1st auto.