Math Problem Statement

Imagine that you are taking a multiple-choice quiz written in Danish and must guess randomly. Each question has 4 choices and 1 correct answer. Please round all answers to four decimal places.

Calculate the probability that you...

answer the first question correctly.

answer the first 2 questions correctly.

answer the first 3 questions correctly.

answer the first 4 questions correctly.

Submit QuestionQuestion 8

Solution

In this case, for each question, there is one correct answer and three incorrect answers, so the probability of answering any given question correctly is:

P(correct answer)=14=0.25P(\text{correct answer}) = \frac{1}{4} = 0.25

And the probability of answering a question incorrectly is:

P(incorrect answer)=34=0.75P(\text{incorrect answer}) = \frac{3}{4} = 0.75

Now, let's calculate the probabilities for each case:

  1. Probability of answering the first question correctly:

    • Since the probability of answering one question correctly is 0.250.25, the probability of answering the first question correctly is:

    P(first question correct)=0.25P(\text{first question correct}) = 0.25

  2. Probability of answering the first 2 questions correctly:

    • The probability of answering both the first and second questions correctly is the product of the probabilities for each:

    P(first 2 correct)=0.25×0.25=0.0625P(\text{first 2 correct}) = 0.25 \times 0.25 = 0.0625

  3. Probability of answering the first 3 questions correctly:

    • Similarly, the probability of answering the first three questions correctly is:

    P(first 3 correct)=0.25×0.25×0.25=0.015625P(\text{first 3 correct}) = 0.25 \times 0.25 \times 0.25 = 0.015625

  4. Probability of answering the first 4 questions correctly:

    • Finally, the probability of answering all four questions correctly is:

    P(first 4 correct)=0.25×0.25×0.25×0.25=0.00390625P(\text{first 4 correct}) = 0.25 \times 0.25 \times 0.25 \times 0.25 = 0.00390625

Now, rounding all the answers to four decimal places:

  1. Probability of answering the first question correctly: 0.2500
  2. Probability of answering the first 2 questions correctly: 0.0625
  3. Probability of answering the first 3 questions correctly: 0.0156
  4. Probability of answering the first 4 questions correctly: 0.0039

Let me know if you'd like further clarification or more details!

5 Related Questions:

  1. What is the probability of answering 5 questions correctly?
  2. If there are 10 questions, what is the probability of answering all 10 correctly?
  3. How does the probability change if there are more than 4 answer choices per question?
  4. What is the probability of answering at least 1 question correctly?
  5. How would the probability be affected if there were 5 choices per question instead of 4?

Tip:

When calculating the probability of multiple independent events happening in sequence (like answering multiple questions correctly), you can multiply the individual probabilities together.

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Math Problem Analysis

Mathematical Concepts

Probability
Independent Events

Formulas

P(correct answer) = 1/4
P(incorrect answer) = 3/4

Theorems

Multiplication Rule for Independent Events

Suitable Grade Level

Grades 7-9