SOLUTION: Hi! I really need your help on this question please! POP QUIZ! On a 20 question multiple choice quiz, you guess at every question. There are five choices for each question. O

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Question 1176459: Hi! I really need your help on this question please!
POP QUIZ! On a 20 question multiple choice quiz, you guess at every question. There are five choices for each question. Only one of the five is the correct answer. What is the probability that you get exactly 2 correct? Give your answer as a decimal rounded to three decimal places.
Thank you so much! Very much appreciated!
Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
.

It is the binomial type probability distribution.


The number of trial n= 20; the probability of the success trial is  1%2F5,  and the number of success trial k = 2. 


    P = C%5B20%5D%5E2%2A%281%2F5%29%5E2%2A%284%2F5%29%5E%2820-2%29 = %28%2820%2A19%29%2F%281%2A2%29%29%2A0.2%5E2%2A0.8%5E18 = 0.136909 = 0.137 (rounded).     ANSWER

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To see many other similar solved problems, look into the lessons
    - Simple and simplest probability problems on Binomial distribution
    - Typical binomial distribution probability problems
in this site.