+0  
 
0
25
1
avatar

A multiple-choice test has 6 questions. Each question has 5 choices and only one of which is correct. If a student guesses the answer for each question find the probability that the students gets exactly 3 questions correct

 Mar 8, 2020
 #1
avatar+1068 
0

There are 6 choose 3 or 20 total arrangements of questions.

The chance that a student gets one right is 1/5 and wrong is 4/5.

Since we want to find 3 questions correct, it is \((\frac{1}{5})^3\times (\frac{4}{5})^3\), or 64/15625

But we have to multiply by 20 to get 1280/15625, simplified to 256/3125.

 

You are very welcome!

:P

 Mar 8, 2020

34 Online Users

avatar
avatar
avatar