Interestingly, we don't have an answer to your question. Our site is so open and available to the people who use it that we don't track this type of information. We have some learners who come in for a quick answer to a question and others who spend days or even weeks reviewing the content over and over again. Even if we had the information, we'd likely never post it on our tutorials because if people saw how long it could take to complete a tutorial in its entirety, it may seem too intimidating and they may never even start!
We do, however, have some data we can share. Based on our analytics, it looks as though the average time spent on a content page is 1:53. So for a tutorial like Computer Basics, which has 77 pages, the length of time to complete this entire tutorial would be around 2.5 hours. We hope this helps!