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.
How many gallons of gasoline are used in US in a day? The official statistics according to the EIA (Energy Information Administration) are that the US uses 9,253,000 barrels/day or 388.6 million gallons/day.