By definition, we have that the conversion of a US gallon to liters is given by:
 1 liter = 3.78541 gallons
 Therefore, we can apply the following rule of three:
 1 liter ---------------------> 3.78541 gallons
 5100 liters --------------> x
 Clearing x we have:
 [tex]x = (5100) * (3.78541)
x = 19305.591[/tex]
 two significant figures:
 [tex]x = 19000
[/tex]
 Answer:
 The lung capacity of the blue whale is:
 [tex]x = 19000 gallons[/tex]