Answer: 4.11 percent of the car's mass is gasoline after filling it up.
Step-by-step explanation:
20.1gallons multiplied by 3.785L/gal multiplied by 0.737kg/L multiplied by 2.20lbs per kg. Then divide by total mass of the car. Add the dry weight plus the weight of the gasoline found to find the total weight. Multiply by 100 to get percent.