The question is about converting 26km^2 with 2 inches of water into acre-feet. I know the answer is 1100 acre-feet but stuck in converting feet into acre-feet. 1 acre = 43560ft^2 1 acre-foot = 1 acre of land and one foot depth. I might be posting here often and just wondering if it's ok. This isn't homework for college or school and I bought a text book by haliday (7th edition) so I can learn physics at home. Thanks for any help.