I found this problem on that other Q&A site (Yahoo! Answers) and thought it was kind of fun to solve. It requires nothing more than the most basic algebra plus a little bit of reasoning and a little bit of effort. The story behind the problem is a bit lame, but I could not think of anything better. If you have an improvement let me know.

Five children are weighed in pairs. Their weights in kg are:
58 60 61 64 64 65 67 68 70 71

What are the five weights?