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?

The second car will produce 50 pounds less carbon than the first auto

Explanation:

Let's begin with the first auto:

if one gallon of fuel is used in 20 miles, in 600 miles the gallons of fuel consumed are (600 miles * 1 gallon / 20 miles) 30. One gallon of fuel produces 5 pounds CO2, then, 30 gallons will produce (30 gallons * 5 pounds CO2 / 1 gallon) 150 pounds CO2.

The second auto uses 1 gallon fuel per 30 miles, then, in 600 miles, it will use (600 miles * 1 gallon / 30 miles) 20 gallons. If one gallon fuel produces 5 pounds CO2, 20 gallons will produce (20 gallons * 5 pounds CO2 / 1 gallon) 100 pounds CO2.

The second car will then produce 50 pounds less carbon than the first auto