# A firkin is an old British unit of volume equal to 9 gal. lons. How many cubic meters are there in 12.4 firkins?

$0.4224 {\text{ m}}^{3}$.
One gallon is $3.785$ liters. One liter is one cubic decimeter (deci is the old metric prefix for one tenth), thus $0.001$ cubic meter. Then
(12.4" firkin")({9 " gal"}/"firkin")({3.785" L"}/"gal")({0.001" m"^3}/"L")=0.4224" m"^3
The numbers $9$ and $12.4$ are treated as exact for this problem, but the conversion factor of $3.785$ liters per gallon is rounded to four significant digits. So the final answer is likewise rounded.