text: The answer requires you to make an assumption about the relative probability of an apprentice compared to a non-apprentice getting injured.  If the chances are equal and independent, then the answer is simply 1/binomial(3,16) = 3!x13!/16!= 1/(7x5x16)\n\nIf the probability of an apprentice being in the wrong place at the wrong time is higher than a non-apprentice, then one can assume that the probability is somewhere between 1/560 and 1.