For the past several semesters, I've been running math study groups with the Duke Academic Resource Center - organized by Ben Cooke. Each week, we go over worksheets containing practice problems and review any material which may have been particularly confusing to students. I've done Multi, Linear Algebra, and Differential Equations. It's really fun for me to be able to help my peers succeed in their math courses and maybe learn some tricks along the way that I maybe hadn't thought of before.
Usually, although I would try my best to answer all questions, people would still want "solutions" to the worksheets either to make sure they did things right, as a study resource, or for some other reason. Sometimes, they would also want an extra copy of the worksheet for a friend. Usually, I would just have them take a photo on their phones, but sometimes they would say something like "I missed last week, do you have the worksheet from last week?". In response, I would sometimes have the requested worksheet handy, but most times I would ask them to write down their email so I could send it to them. This semester, I decided it may be easier to make them available online.
Originally, I wanted to use a URL shortener and link the worksheets as well as scanned copies of my solutions, but when I sat down to start making URLs, I realized it would be a nightmare to keep track of all the URLs and write them on the board all the time. Well, since I just happened to have
Now that they're posted at gerry-chen.com/studygroups, I should address the fact that I did not actually check with Ben Cooke to make sure this would be okay with him. I know that he has generally been against providing official solutions for a number of reasons, including but not limited to (1) not wanting to be responsible for wrong ansswers, (2) discouraging skipping the sessions and just using the worksheets/solutions online, and (3) reducing collaboration. Nonetheless, I'm hoping the relatively recluse existence of these should minimize issues that arise, and I can always take down the site in a jiffy should problems arise.