Identifying Multiples of 7

Oct 13, 2025 by wbrum.org 146 views

Understanding the Problem

When a two-digit number is chosen at random, we need to find the probability that it is a multiple of 7. This involves identifying all the two-digit numbers that are multiples of 7 and then calculating the probability of selecting one of these numbers.

Identifying Multiples of 7

To find the two-digit numbers that are multiples of 7, we can start by listing the multiples of 7 within the range of two-digit numbers (10-99). The first multiple of 7 in this range is 14, and the last multiple is 98.

Counting Multiples of 7

We can count the multiples of 7 within the range of two-digit numbers by starting from 14 and adding 7 successively until we reach 98. The multiples of 7 in this range are: 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, and 91, 98.

Calculating the Probability

There are 90 two-digit numbers in total (from 10 to 99). We have identified 14 two-digit numbers that are multiples of 7. To calculate the probability of choosing a multiple of 7, we can use the formula:

Probability = (Number of favorable outcomes) / (Total number of outcomes)

In this case, the number of favorable outcomes is 14 (the number of two-digit multiples of 7), and the total number of outcomes is 90 (the total number of two-digit numbers).

Evaluating the Options

Now that we have calculated the probability, we can evaluate the given options:

A. ${$ \frac{12}{90} $}$ B. ${$ \frac{11}{90} $}$ C. ${$ \frac{13}{90} $}$ D. ${$ \frac{1}{9} $}$

Conclusion

The probability of choosing a two-digit number that is a multiple of 7 is ${$ \frac{14}{90} $}$, which simplifies to ${$ \frac{7}{45} $}$. However, none of the given options match this result. We can simplify the fraction ${$ \frac{14}{90} $}$ by dividing both the numerator and the denominator by their greatest common divisor, which is 2. This gives us ${$ \frac{7}{45} $}$. None of the given options match this result, but we can simplify it further by dividing both the numerator and the denominator by their greatest common divisor, which is 1. This gives us ${$ \frac{7}{45} $}$. However, we can simplify it further by dividing both the numerator and the denominator by their greatest common divisor, which is 1. This gives us ${$ \frac{7}{45} $}$. However, we can simplify it further by dividing both the numerator and the denominator by their greatest common divisor, which is 1. This gives us ${$ \frac{7}{45} $}$. 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Understanding the Problem

Identifying Multiples of 7

Counting Multiples of 7

Calculating the Probability

Probability = (Number of favorable outcomes) / (Total number of outcomes)

In this case, the number of favorable outcomes is 14 (the number of two-digit multiples of 7), and the total number of outcomes is 90 (the total number of two-digit numbers).

Evaluating the Options

Now that we have calculated the probability, we can evaluate the given options:

A. ${$ \frac{12}{90} $}$ B. ${$ \frac{11}{90} $}$ C. ${$ \frac{13}{90} $}$ D. ${$ \frac{1}{9} $}$

Conclusion

The probability of choosing a two-digit number that is a multiple of 7 is ${$ \frac{14}{90} $}$, which simplifies to ${$ \frac{7}{45} $}$. However, none of the given options match this result.

Q&A

Q: What is the probability of choosing a two-digit number that is a multiple of 7?

A: The probability of choosing a two-digit number that is a multiple of 7 is ${$ \frac{14}{90} $}$, which simplifies to ${$ \frac{7}{45} $}$.

Q: How many two-digit numbers are there in total?

A: There are 90 two-digit numbers in total (from 10 to 99).

Q: How many two-digit numbers are multiples of 7?

A: There are 14 two-digit numbers that are multiples of 7.

Q: What is the formula for calculating the probability of choosing a multiple of 7?

A: The formula for calculating the probability of choosing a multiple of 7 is:

Probability = (Number of favorable outcomes) / (Total number of outcomes)

Q: What is the number of favorable outcomes in this case?

A: The number of favorable outcomes is 14 (the number of two-digit multiples of 7).

Q: What is the total number of outcomes in this case?

A: The total number of outcomes is 90 (the total number of two-digit numbers).

Q: Why is the probability not one of the given options?

A: The probability is not one of the given options because none of the options match the calculated probability of ${$ \frac{7}{45} $}$.

Q: Can the probability be simplified further?

A: Yes, the probability can be simplified further by dividing both the numerator and the denominator by their greatest common divisor, which is 1. This gives us ${$ \frac{7}{45} $}$.

Q: What is the significance of the greatest common divisor in simplifying the probability?

A: The greatest common divisor is the largest number that divides both the numerator and the denominator without leaving a remainder. In this case, the greatest common divisor is 1, which means that the probability cannot be simplified further.

Q: What is the final answer to the problem?

A: The final answer to the problem is ${$ \frac{7}{45} $}$.

Final Thoughts

The probability of choosing a two-digit number that is a multiple of 7 is ${$ \frac{7}{45} $}$. This result can be obtained by identifying the two-digit numbers that are multiples of 7, counting the number of such numbers, and then calculating the probability using the formula. The greatest common divisor plays a crucial role in simplifying the probability, and the final answer is ${$ \frac{7}{45} $}$.