It depends. Is it 391 pounds of foam, or 391 pounds of gasoline, or 391 pounds of uranium, or what?
42 gallons of water is 350.7 pounds
10 US gallons is approximately 83.5 pounds
30 pounds of water is 3.593 gallons.
About 250.5 pounds for 30 US gallons.
10 gallons of water is 83.5 pounds
800 pounds of water would be 95.8 US 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.
20 gallons of water weighs 167 pounds.
4o pounds
15,820 gallons of water weighs 132,097 pounds.
417.5 pounds for 50 US gallons.
About 25 pounds for three US gallons of water.