In a quiz contest, Mary answers 90% of the questions correctly without any additional clues from the quiz coordinator. The randomly generated numbers below simulate this situation.
The numbers 0 to 8 represent questions answered correctly without additional clues, and the number 9 represents questions that needed additional clues.
44 51 99 66 23
68 72 20 20 59
50 89 39 36 20
90 13 51 47 92
49 20 89 10 13
52 82 52 52 99
28 10 33 35 73
40 44 30 95 22
99 10 55 10 35
36 78 92 37 96
The estimated probability that it would take at least three questions for Mary to need additional clues is
.
The estimated probability that Mary needed additional clues to answer two consecutive questions is
.
Answers
To solve this problem, we should note that there are:
total questions = 100
questions answered correctly = 90
questions that needed additional clues = 10
1. The first question is to find the probability that in the third question, Mary would need additional clue. Therefore this implies that in the first and second questions, Mary would answer it correctly. Therefore:
Probability = (question 1 answered correctly) * (question 2 answered correctly) * (question 3 needed clue)
Probability = (90/100)*(89/99)*(10/98)
Probability = 0.08256 = 8.26%
2. The second question finds for the probability that two consecutive needs additional clue, therefore:
Probability = (question 1 needed clue) * (question 2 needed clue)
Probability = (10/100)*(9/99)
Probability = 9.1*10^-3 = 0.91%