guys, 1/4 and 25% are both correct and were marked as incorrect. Either provide more detail on format for answers, or make the evaluation function smarter.
@Cart, I added text that explains if an exact answer is needed for the question or if a 'math answer' (like 1/4 or 10!) is good too.
same as last problem
You don't specify that the first coin is replaced which would influence the probability of selection of the unbiased coin.