First let us make all the units constant. I am going to convert all the units into inches.

Therefore, the dimensions of the cylinder are:

Diameter = 4 inches

Length = 1 foot = 12 inches

Let's find its volume now:

Volume = base area x height

Base Area = pi x r

= 3.14 x (4/2)

= 3.14 x 2

= 3.14 x 4

= 12.56 inch

Volume = 12.56 x 12

= 150.72 inch

This is the volume in cubic inches. To find the volume in gallons, divide this answer by 231.

Volume in gallons = 150.72/231

= 0.65 gallons

Therefore, there are 0.65 gallons of water in the cylinder.

Therefore, the dimensions of the cylinder are:

Diameter = 4 inches

Length = 1 foot = 12 inches

Let's find its volume now:

Volume = base area x height

Base Area = pi x r

^{2}= 3.14 x (4/2)

^{2}= 3.14 x 2

^{2}= 3.14 x 4

= 12.56 inch

^{2}Volume = 12.56 x 12

= 150.72 inch

^{3}This is the volume in cubic inches. To find the volume in gallons, divide this answer by 231.

Volume in gallons = 150.72/231

= 0.65 gallons

Therefore, there are 0.65 gallons of water in the cylinder.