The Divisibility Rule of 11

Oct 13, 2025 by wbrum.org 9 views

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Introduction

In mathematics, the divisibility rule of 11 is a simple yet powerful tool used to determine whether a given number is divisible by 11 or not. This rule is based on the concept of alternating the addition and subtraction of the digits of the number. In this article, we will delve into the world of divisibility rules and explore the concept of divisibility by 11 in detail.

What is Divisibility by 11?

Divisibility by 11 is a fundamental concept in mathematics that helps us determine whether a given number is divisible by 11 or not. A number is said to be divisible by 11 if it can be divided by 11 without leaving a remainder. In other words, if a number is divisible by 11, it can be expressed as a product of 11 and another integer.

The Divisibility Rule of 11

The divisibility rule of 11 is based on the concept of alternating the addition and subtraction of the digits of the number. To apply this rule, we need to follow these steps:

Take the given number and write its digits in a row.
Alternate the addition and subtraction of the digits, starting with addition.
If the result is a multiple of 11, then the number is divisible by 11.

Applying the Divisibility Rule of 11

Let's apply the divisibility rule of 11 to the number 1y3y6. To do this, we need to alternate the addition and subtraction of the digits, starting with addition.

Add the first and third digits: 1 + 3 = 4
Subtract the second digit: 4 - y
Add the fourth and sixth digits: 3 + 6 = 9
Subtract the result from step 2 from the result in step 3: 9 - (4 - y) = 5 + y

Solving for y

Now that we have the expression 5 + y, we need to find the value of y that makes this expression a multiple of 11. To do this, we can set up an equation:

5 + y = 11k

where k is an integer.

Finding the Value of y

To find the value of y, we can try different values of k and see which one gives us a valid value for y.

If k = 1, then 5 + y = 11(1) = 11, which gives us y = 6.
If k = 2, then 5 + y = 11(2) = 22, which gives us y = 17.
If k = 3, then 5 + y = 11(3) = 33, which gives us y = 28.

Conclusion

In conclusion, the value of y that makes the number 1y3y6 divisible by 11 is 6. This is because when we substitute y = 6 into the expression 5 + y, we get 5 + 6 = 11, which is a multiple of 11.

Final Answer

The final answer is 6.

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Q&A: Divisibility Rule of 11

Q1: What is the divisibility rule of 11?

A1: The divisibility rule of 11 is a simple yet powerful tool used to determine whether a given number is divisible by 11 or not. This rule is based on the concept of alternating the addition and subtraction of the digits of the number.

Q2: How do I apply the divisibility rule of 11?

A2: To apply the divisibility rule of 11, you need to follow these steps:

Take the given number and write its digits in a row.
Alternate the addition and subtraction of the digits, starting with addition.
If the result is a multiple of 11, then the number is divisible by 11.

Q3: What is the significance of the alternating addition and subtraction in the divisibility rule of 11?

A3: The alternating addition and subtraction in the divisibility rule of 11 is a key concept that helps us determine whether a number is divisible by 11 or not. By alternating the addition and subtraction of the digits, we can simplify the calculation and make it easier to determine whether the number is divisible by 11.

Q4: Can you give an example of how to apply the divisibility rule of 11?

A4: Let's consider the number 1y3y6. To apply the divisibility rule of 11, we need to alternate the addition and subtraction of the digits, starting with addition.

Add the first and third digits: 1 + 3 = 4
Subtract the second digit: 4 - y
Add the fourth and sixth digits: 3 + 6 = 9
Subtract the result from step 2 from the result in step 3: 9 - (4 - y) = 5 + y

Q5: How do I find the value of y that makes the number 1y3y6 divisible by 11?

A5: To find the value of y, we can set up an equation:

5 + y = 11k

where k is an integer.

We can try different values of k and see which one gives us a valid value for y.

If k = 1, then 5 + y = 11(1) = 11, which gives us y = 6.
If k = 2, then 5 + y = 11(2) = 22, which gives us y = 17.
If k = 3, then 5 + y = 11(3) = 33, which gives us y = 28.

Q6: What is the final answer for the value of y that makes the number 1y3y6 divisible by 11?

A6: The final answer is 6.

Q7: Can you explain why the value of y is 6?

A7: Yes, when we substitute y = 6 into the expression 5 + y, we get 5 + 6 = 11, which is a multiple of 11. Therefore, the value of y that makes the number 1y3y6 divisible by 11 is 6.

Q8: How can I use the divisibility rule of 11 in real-life situations?

A8: The divisibility rule of 11 can be used in a variety of real-life situations, such as:

Checking whether a number is divisible by 11 in a mathematical problem or puzzle.
Verifying whether a number is a multiple of 11 in a financial or accounting context.
Using the divisibility rule of 11 to simplify calculations and make it easier to determine whether a number is divisible by 11.

Q9: Are there any other divisibility rules that I should know about?

A9: Yes, there are several other divisibility rules that you should know about, including:

The divisibility rule of 2: A number is divisible by 2 if its last digit is even (0, 2, 4, 6, or 8).
The divisibility rule of 3: A number is divisible by 3 if the sum of its digits is a multiple of 3.
The divisibility rule of 5: A number is divisible by 5 if its last digit is 0 or 5.

Q10: Can you provide more examples of how to apply the divisibility rule of 11?

A10: Yes, here are a few more examples of how to apply the divisibility rule of 11:

Consider the number 245. To apply the divisibility rule of 11, we need to alternate the addition and subtraction of the digits, starting with addition.

Add the first and third digits: 2 + 5 = 7
Subtract the second digit: 7 - 4 = 3
Add the result from step 2 to the last digit: 3 + 5 = 8

Since the result is not a multiple of 11, the number 245 is not divisible by 11.

Consider the number 363. To apply the divisibility rule of 11, we need to alternate the addition and subtraction of the digits, starting with addition.

Add the first and third digits: 3 + 6 = 9
Subtract the second digit: 9 - 3 = 6
Add the result from step 2 to the last digit: 6 + 3 = 9

Since the result is a multiple of 11, the number 363 is divisible by 11.