Final answer:
A barrel of oil, which is 42 gallons, converts to approximately 159 liters when using the conversion rate of 1 gallon being equivalent to 3.78541 liters (a).
Step-by-step explanation:
A barrel of oil is exactly 42 gallons, and the question is asking how many liters are in a barrel. To make this conversion, we use the equivalence that 1 U.S. gallon is approximately equal to 3.78541 liters. Therefore, to find the number of liters in a barrel, we multiply 42 gallons by 3.78541 liters per gallon.
The calculation would look like this:
42 gal x 3.78541 L/gal = 158.78722 L
When rounded to the nearest whole number, since standard practice in these measurements is to use whole liters, we get approximately 159 liters. This rounding is consistent with industry standards, where a barrel of petroleum is equated to 159 L.