a scientist used a unique two - color code to identify each of the test subjects involved in a certain study . if the scientist found that choosing from among 5 colors produced enough color codes to identify all but 6 of the test subjects , how many test subjects were in the study ? ( assume that the order of the colors in the codes does not matter . )
5 c 2 = 10 the number of test subjects is 10 + 6 = 16 the answer is c .
add(divide(factorial(5), multiply(factorial(subtract(5, const_2)), factorial(const_2))), 6)