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A quiz contains 5 true/false questions and 5 multiple-choice questions, where each multiple-choice question has 4 choices. If you randomly guess on each question, what is the probability of missing at least one question?

A. 97.664%
B. 99.091%
C. 99.997%
D. 98.230%
E. 95.411%

User Seishin
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1 Answer

5 votes

Final answer:

The probability of missing at least one question on a quiz with 5 true/false and 5 multiple-choice questions, when guessing randomly, is approximately 99.997%, corresponding to answer choice C.

Step-by-step explanation:

To calculate the probability of missing at least one question:

  1. Calculate the probability of getting a question right:
  • True/False question: 1/2 chance of guessing correctly.
  • Multiple-choice question with 4 choices: 1/4 chance of guessing correctly.
Calculate the probability of guessing all questions right:
  • Probability of guessing all true/false questions correctly: (1/2)^5.
  • Probability of guessing all multiple-choice questions correctly: (1/4)^5.
  • Total probability of guessing all questions correctly: (1/2)^5 * (1/4)^5.
Find the complementary probability of not guessing all questions correctly, which gives us the probability of missing at least one question.
  • Complementary probability: 1 - ((1/2)^5 * (1/4)^5).
  • Perform the calculation: 1 - (1/32 * 1/1024).
  • This equals 1 - (1/32768), which simplifies to 32767/32768.
  • Convert to a percentage: (32767/32768) * 100%, roughly 99.997%.

Therefore, the probability of missing at least one question when randomly guessing is approximately 99.997%, which corresponds to answer choice C.

User Alpants
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