Question 92750
there are 15 questions with 3 possible choices for each, this means that there are 3^15 different combinations of answers


a.) assuming only one correct choice for each question, there is only ONE combination of all correct answers (1^15)


b.)  the number of different groups of 4 items contained in a group of 15 is (15*14*13*12)/(4*3*2*1) ... there are 15 ways to select the first item, 14 ways to select the second, etc. ... the numerator of the expression results from the fact that order is NOT important ... a,b,c,d is the same group as b,a,d,c


c.) there are 15 questions with 2 possible wrong choices for each, this means that there are 2^15 ways to get EVERY question wrong ... since there are 3^15 combinations of answers, there are ((3^15)-(2^15)) ways to get at least one item correct