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Express all probabilities as fractions. A thief steals an ATM card and must randomly guess the correct pin code that consists of four digits (each 0 through 9 ) that must be entered in the correct order. Repetition of digits is allowed. What is the probability of a correct guess on the first try?

Short Answer

Expert verified
\( \frac{1}{10,000} \)

Step by step solution

01

Determine the total number of possible PIN codes

Each digit in the PIN code can be any digit from 0 to 9, which means there are 10 choices for each of the 4 digits. Calculating the total number of possible PIN codes involves multiplying the number of choices for each digit together: \[ 10 \times 10 \times 10 \times 10 = 10^4 = 10,000 \]
02

Identify the number of successful outcomes

There is only one successful outcome, which is guessing the correct PIN code on the first try. Thus, the number of successful outcomes is 1.
03

Calculate the probability of the correct guess

The probability of guessing the correct PIN code is given by the ratio of the number of successful outcomes to the total number of possible outcomes. Therefore, the probability \( P \) is: \[ P = \frac{1 \text{ successful outcome}}{10,000 \text{ possible outcomes}} = \frac{1}{10,000} \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

probability calculation
Probability in statistics measures how likely an event is to occur. It is calculated using the ratio of the number of successful outcomes to the number of possible outcomes.
In our case, the successful outcome is guessing the correct PIN on the first try. The probability calculation formula is:
\(
\text{Probability} = \frac{\text{Number of Successful Outcomes}}{\text{Total Number of Possible Outcomes}}
\)
To express probabilities as fractions helps in maintaining accuracy and simplicity, which is important in statistical computations.
possible outcomes
Possible outcomes refer to all the different ways an event can occur. For a PIN with four digits where each digit can be any from 0 to 9, we need to calculate the total number of combinations.
Each of the 4 digits in the PIN can independently be any of the 10 digits. This leads to:
\[ 10^4 = 10,000 \]
possible combinations.
Thus, there are 10,000 possible outcomes for the PIN guesses.
successful outcomes
A successful outcome is the specific result we are interested in. In the context of our problem, a successful outcome is guessing the exact PIN correctly on the first try.
Since there is only one correct PIN from the 10,000 possible PINs, we have only one successful outcome.
This is crucial for determining the probability, as all probabilities hinge on the number of successful outcomes relative to possible outcomes.
random guessing
When guessing randomly, each possible outcome has an equal chance of being selected.
In the problem, the thief does not have any clues about the PIN. Therefore, each of the 10,000 possible PIN codes is equally likely.
This concept of random guessing is important because:
  • It ensures that the probability calculation is fair.
  • Each PIN has an equal chance of being the correct one.
Thus, the probability of correctly guessing the PIN on the first try is simply the fraction of one successful outcome over 10,000 possible outcomes:
\[ \frac{1}{10,000} \].

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