I submitted a cute probability problem to the Riddler section of Nate Silver’s Five Thirty Eight web site. Here’s a cut-and-paste of the problem.
From Steve Simon, an adorable living-room puzzle:
Your baby is learning to walk. The baby begins by holding onto a couch. Whenever she is next to the couch, there is a 25 percent chance that she will take a step forward and a 75 percent chance that she will stay clutching the couch. If the baby is one or more steps away from the couch, there’s a 25 percent chance that she will take a step forward, a 25 percent chance she’ll stay in place and a 50 percent chance she’ll take one step back toward the couch.
In the long run, what percent of the time does the baby choose to clutch the couch?
You can find an earlier version of this page on my blog.