Posted by **HM** on Wednesday, November 9, 2011 at 4:18am.

An unprepared student makes random guesses for the ten true-false questions on a quiz. Find the probability that there is at least one correct answer.

Could some one please help me?

And explain to me how they got the answer?

and is there another way besides the tree method?

- PROBABILITY MATH -
**Reiny**, Wednesday, November 9, 2011 at 8:08am
All we have to exclude is the case when he guessed all of them wrong

that prob would be (1/2)^10 = 1/1024

so the prob of getting at least one correct is 1 - 1/1024 = 1023/1024

- PROBABILITY MATH -
**ebony**, Monday, May 14, 2012 at 12:28am
Take 10/2=5

possibility of 5 right or 5 wrong because there is only two possible outcomes

2/100 = .50 (True and False Outcomes)

There are a total of 10 questions

.50^10 questions = .0009765625 rounded = .0009777

use the complement formula 1-P=

1-.0009777 = .9990223 that there is at least once correct answer

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