Math Problem Statement
"An ordinary fair die is thrown repeatedly until a 6 is obtained. Find the probability that it takes at least 3 throws but no more than 5 throws to obtain a 1 or 6."
Solution
To solve this problem, we'll break it down step by step:
Step 1: Define the Situation
- We are rolling a fair die repeatedly until a 6 is obtained.
- We want to find the probability that it takes at least 3 throws but no more than 5 throws to obtain a 1 or a 6.
Step 2: Identify the Probabilities
- The probability of rolling a 1 or a 6 on any single throw is .
- The probability of not rolling a 1 or a 6 (i.e., rolling a 2, 3, 4, or 5) on any single throw is .
Step 3: Set Up the Events
We need to calculate the probability of getting either a 1 or a 6 on the 3rd, 4th, or 5th throw, with no such result before.
- At least 3 throws means that for the first two throws, neither a 1 nor a 6 is rolled. The probability for each of these throws is .
- The final throw (3rd, 4th, or 5th) must result in either a 1 or a 6, with probability .
Step 4: Calculate the Desired Probability
We calculate the probabilities for each of the events where the 1st and 2nd rolls result in a non-1/6 outcome, followed by a success on the 3rd, 4th, or 5th roll.
- Probability of success on the 3rd throw:
- Probability of success on the 4th throw:
- Probability of success on the 5th throw:
Step 5: Add the Probabilities Together
The total probability is the sum of the individual probabilities:
Now, let's calculate this.The probability that it takes at least 3 throws but no more than 5 throws to obtain a 1 or a 6 is approximately 0.313 or 31.3%.
Would you like further details on the solution or have any other questions?
Here are 5 related questions to further explore:
- How would the probability change if we were interested in at least 4 throws but no more than 6 throws?
- What is the expected number of throws needed to get a 1 or a 6?
- How would the probability differ if the die were biased, favoring some outcomes over others?
- What is the probability that a 1 or a 6 is rolled on the first throw?
- How would the total probability change if we consider two dice instead of one?
Tip: When solving probability problems involving multiple independent events, it is helpful to first break down the individual probabilities and then combine them using addition or multiplication rules.
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Math Problem Analysis
Mathematical Concepts
Probability
Independent Events
Formulas
P(Success on nth throw) = (2/3)^(n-1) * (1/3)
Total Probability = P(Success on 3rd throw) + P(Success on 4th throw) + P(Success on 5th throw)
Theorems
Multiplication Rule of Probability
Addition Rule of Probability
Suitable Grade Level
Grades 10-12
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