First, you find what 20% of 10 gallons of gas would be. This will show how many gallons the car actually uses. 10 gallons x 20% = 10 x 0.20 = 2 gallons used
Then you subtract that number from the total 10 gallons to get how many gallons of gas would be wasted. 10 gallons - 2 gallons = 8 gallons of gas wasted
If a car has an energy efficiency of 20% and you put in 10 gallons of gas, then 2 gallons are used effectively, and 8 gallons are wasted. This shows that a significant amount of fuel goes unused due to inefficiencies in the system.
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