The conversion factors are 42 gallons in a barrel
4 quarts = 1 gallon. I use unit analysis to get answers for questions like these.
[tex]\dfrac{120barrels}{1} * \dfrac{42 gallons}{1 barrel} * \dfrac{4 quarts}{1 gallon} [/tex]
All the units are in the numerator. There are 120 * 42* 4 = 20160 quarts in 120 barrels.
