A guy I used to work with is married to a math teacher. Once in a while I would send him a math problem I'd thought of that might be interesting to high school math students.
I noticed he isn't on my facebook friends any more. I guess he deleted his account or just deleted me as a fb friend. oh well he'd been among my first 20 or so friends back in like 2007. If he deleted me then no biggie.
I checked I have 141 fb friends at this moment. Of these I could delete about 30 today and it wouldn't make any difference in my facebook experience. People I don't know, people I don't really like, people I don't care about. But if you're on my fb and you're reading this then you're on my "good" list lol.
Anyway back to the math problem I was going to send. Suppose you have a hardware random number generator call it R. It has the property that it will return a uniformly distributed random number in the range [0, 1).
Suppose you are working on an application of some type such as a game and the design requires a random number in the range of 0.10 to 0.85. How do you get this using the generator R?
As a further constraint let's say that you are in a resource constrained environment such as on a battery operated mobile phone. So for performance and battery life you may only invoke R once for this. Thus the scheme of invoking R, and keep repeating until the value returned by R is between 0.10 - 0.85 is not acceptable. It is unacceptable because 25% of the time you would have to invoke R more than once.
It's not a real difficult problem in my opinion. I'll let it sit for a bit and post a solution I came up with in the comments.