An estimate would be 2 and 1/2 gallons. Pounds is a unit of mass/weight. Gallons is a liquid measure. They do not convert cleanly. The density of the liquid being measured can make a big difference. If the liquid is water, there is 8 pounds to a gallon.
A gallon of water is estimated to weigh 8.34 pounds. 21 tons divided by 8.34 pounds = 5035.97122 gallons of water.
Twenty liters is 5.3 US gallons.
It depends upon the size of the pelican and the sizes of the fish.
42 gallons of water is 350.7 pounds
10 US gallons is approximately 83.5 pounds
10 gallons of water is 83.5 pounds
30 pounds of water is 3.593 gallons.
6 and 1 half gallons
That depends on what substance you have 227.5 pounds of.227.5 pounds of air fills many, many gallons.227.5 pounds of water fills about 27.2 gallons.227.5 pounds of granite fills only a few gallons.
4o pounds
20 gallons of water weighs 167 pounds.
417.5 pounds for 50 US gallons.