we know that
[volume of a cylindrical paint can 1]=[area of the base]*h
so
[area of the base]*h=1 gallon
if the height is doubled
[volume of a cylindrical paint can 2]=[area of the base]*(2*h)
[volume of a cylindrical paint can 2]=2*{[area of the base]*h)}
[volume of a cylindrical paint can 2]=2*[volume of a cylindrical paint can 1]
[volume of a cylindrical paint can 2]=2*[1 gallon]-----> 2 gallons
the answer is
the capacity of the lager one is 2 gallons