Question

Question 18 3 points Save A In a multiple choice test there are 10 questions and each question is worth 3 marks. Each question has 5 choices, one of which is correct. Assume that Ahmed (who knows nothing) guesses at each answer. If 90% and above is the A grade, determine the probability that he will get A grade. |3 MARKSI 0.1250654345 0.0000041984 0.0055124341 0.999995801

Answer 1

Total marks in the paper is: 10* 3 =30

The 90% of 30 is = 30*0.90 = 27

That is to get grade A Ahmed need to solve at least 27 /3 = 9 question correctly.

Let X is a random variable shows the number of correct answers out of 10. Here X has binomial distribution with parameters as follow:

n = 10 and p = 1/5 = 0.20

The required probability is

10 / 0.0000041984 (0.20)"(1-0.20) 10-r PlX 29-eC)

Hence, second option is correct.