If you have a gallon, you only can have one gallon.
About 240 gallons.
A 20 Gallon tank can hold up to 20 gallons of water.
7.48 gallons
1000000 gallons 10^6
21.1 gallons
About 3.5 gallons. 1 gallon of water = 8.34lbs
5 gallons
1
9200 Gallons
It's about 2000.
1