Hey, I have good news for you. I just tried those practice problems and timed myself to see if I could give you something to compare to (and for fun). I completed the first four in about an hour and 10 minutes (though I am a bit out of practice). Those practice problems are not trivial; they take some thought. I didn't have to use any outside resources, but I did have to test quite a few things out in the terminal as I was coding it.

For background: I am self taught, but I've been programming for almost 2 years. I have done freelance rails programming. I have built multiple rails apps from the ground up by myself. One of these is still in use by multimillion dollar company as a part of their client onboarding program. I've been offered a job as a rails developer, though I didn't end up taking it as I had a higher paying offer on the business end of things.

So I say don't worry if you have a bit of trouble with it. If you felt like you were looking things up all the time, then you just need some more practice. For the algorithm design part (especially the mathy ones), look into Project Euler. It's a great list of problems to get practice and you can use whatever language you want to find the answer, so use Ruby. Practice taking the problems apart into pieces, using helper functions, and writing the pseudocode before you actually code anything. That will make this style of thinking feel more natural.

Feel free to PM me if you want to talk more.