The classic way to convey the error that exists in a measurement is a formula that shows the obtained measurement (X) as a sum of a true score plus some error. One version of this formula is: X = T + e. With this formula in mind, obtaining more precise measures depends on reducing error.
  Mega is the prefix meaning one million, therefore there are one million (1,000,000) gallons in a mega gallon.
The 2015 Chevrolet Colorado has an EPA-estimated mileage of 27 miles per gallon on highways and 20 miles per gallon for city driving. The Colorado has a 21-gallon gas tank.