What is the fine-grained topic of the following text: Then i took 2 on one side and placed it on the other side.Then i took of the heavier 2.Then I did I did one on each side and took off the heavier one .That one told me which one was the heavier and it showed me the lightest bag.In 3 weighings was my solution. Only return the topic.
Solving a weight comparison problem.