SOLUTION: The directions say,"In exercise 2, consider a 10-question true/false test." The question is, 'How many ways are there to score exactly 80%? That is, how many ways are there to get

Algebra ->  Probability-and-statistics -> SOLUTION: The directions say,"In exercise 2, consider a 10-question true/false test." The question is, 'How many ways are there to score exactly 80%? That is, how many ways are there to get       Log On


   

Question 159742: The directions say,"In exercise 2, consider a 10-question true/false test." The question is, 'How many ways are there to score exactly 80%? That is, how many ways are there to get exactly 2 questions wrong? Explain why choosing which questions you will get wrong determines all your answers.'
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The directions say,"In exercise 2, consider a 10-question true/false test." The question is, 'How many ways are there to score exactly 80%? That is, how many ways are there to get exactly 2 questions wrong? Explain why choosing which questions you will get wrong determines all your answers.
---------------
True/False questions are binomial because there are only two possible answers.
-------------
2 wrong out of 10 is the same as 8 right out of 10
---------------
Ans: # of ways to select 2 from 10 is 10C2 = [10*9]/[1*2] = 45
-------------------------------------------
Cheers,
Stan H.