Anticipated Student Response for Open Ended Probability Problem

EXAMPLE 2
In trying to figure out the mathematical probability of passing the 5 question T/F quiz, I realized that since each answer has two outcomes, it's kind of like flipping 5 coins when you get heads or tails for each coin.  I remembered that you can multiply the outcomes (in this case--two) for each event (answer) to find the total possible ways to answer the quiz.  When I mulitplied 2 X 2 X 2 X 2 X 2, which is 2 to the 5th power, not 2 times 5, I got 32.  That means there are 32 possible ways to answer the quiz.  Only one of those ways would make all 5 answers correct, giving you 100%.  Then I had to figure out how many ways you could miss one question and still get a passing grade of 80%.  I decided to list the ways in which one answer is wrong and the other four answers are correct:
      WRRRR     RWRRR     RRWRR     RRRWR     RRRRW
By adding the 5 possible ways to get an 80% and the 1 way to get 100%, I found the total ways to pass is 6.  Therefore, the probability of passing the quiz is only 6/32 or .19 or 19%.  

See the corresponding Probability Lesson Plan
Created by Alice Gabbard