pacifist85
In how many ways can a teacher write an answer key for a mini-quiz that contains 3 true-false questions followed by 2 multiples-choice questions with 4 answer choices each, if the correct answers to all true-false questions cannot be the same?
A. 88
B. 90
C. 96
D. 98
E. 102
Hello, I ended up in the same answer, but I think that I read the question in a totally different way... Your opinion on this would be very useful!
I used this way (trying to arrange the questions in an answer sheet):
We have 3 TF questions and 2 MC questions, which have 4 answer choices each.
The TF questions could be arranged in 3 different ways. Each one of them 1st, 2nd or 3rd
Each MC question could be arranged in 4*4= 16 ways. So, the 2 MC questions in 16*2= 32 ways.
So, 3*32= 96
Ws
Was this just a lucky mistake?
Thank you.
This is wrong. We have 3 true-false questions followed by 2 multiples-choice questions with 4 answer choices each:
Q1: ?
Answer: True or False
Q2: ?
Answer: True or False
Q3: ?
Answer: True or False
M1: ?
Answer: A, B, C, or D
M2: ?
Answer: A, B, C, or D
So, the answer key could be: TTF - AB, FTT - AA, ...
For 3 true-false questions there are 2*2*2 = 8 combinations possible but since we are told that the correct answers to all true-false questions cannot be the same, then we should subtract the cases TTT and FFF, so for 3 true-false questions we get 8 - 2 = 6 combinations.
For 2 multiples-choice questions with 4 answer choices each there are 4*4 = 16 combinations possible.
Thus there are total of 6*16 ways a teacher can write an answer key for the quiz.
Answer: C.
Hope it's clear.