Philip ran out of time while taking a multiple-choice test and plans to guess on the last 4 questions. Each question has 5 possible choices, one of which is correct. Assume that the results of his guesses are independent. What is the probability that he answers exactly 1 question correctly in the last 4 questions?

Guest Jan 22, 2020

#1**0 **

- There are 4 questions with 5 choices each which means that he's got a 1 in 5 chance or 20% chance of getting the answer correct pr.question.

There's a 1 in 20 choice or 5% choice in the pool in total...

But in total there's a total of 4 correct answers out of 20 possible choices.

That is a 4 in 20 or a 1 in 5 chance or 20% chance in total.

Alternatively, on a test with 40 questions there is a 1 in 4 or 25% chance that he gets either question Nr.37., Nr.38., Nr.39. or Nr.40. correct.

Hope that helped?

Kind regards...

BizzyX

BizzyX Jan 22, 2020

#2**+1 **

Philip ran out of time while taking a multiple-choice test and plans to guess on the last 4 questions. Each question has 5 possible choices, one of which is correct. Assume that the results of his guesses are independent. What is the probability that he answers exactly 1 question correctly in the last 4 questions?

P(correct)=0.2

P(exactly one out of 4 correct) = 4C1*0.2*0.8^3 = 4*0.2*0.512 = 0.4096

Melody Jan 27, 2020