One day your teacher surprised you with a 22-question multiple-choice

Alaina Ortiz

Alaina Ortiz

Answered question

2022-02-12

One day your teacher surprised you with a 22-question multiple-choice quiz. Each question has 4 possible answers, only one of which is correct. What is the probability that you will guess at least 1 correctly?

Answer & Explanation

Finn Lucero

Finn Lucero

Beginner2022-02-13Added 17 answers

Step 1
The probability of "at least 1 correctly" means:
1, or 2, or 3, 4, or 22 correct
This would be very tedious to work out.
However, the only outcome not included is the probability of none correct.
P(Pnone correct)=P((all wrong)
=P(W×W×W×W×W×W for 22 questions
For each question,:
P(correct)=14 and P(wrong)=34
P(all wrong)=34×34×34,×34 for 22 questions
P(all wrong)=(34)22
The sum of all the probabilities is always 1
P(at least 1 correct)=1P(all wrong)
=1(34)22
=0.998
This means a 99.8% chance of at least one question being correct,

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