If I have two bottles that I have to fill with water and they can contain 3lbs and 5lbs. And they have no markings how can I get 4lbs?

Answer 1

1. Fill 5 lb container
2. Fill 3 lb container from 5lb, leaving 2 lb in 5 lb container
3. Empty 3 lb container
4. Pour contents (2 lb) of 5 lb container into 3 lb container
5. Fill 5 lb container
6. Top up 3 lb container (with 1lb) from 5 lb container to fill 3 lb container.
7. Leavers 4lb in 5 lb container.