204 LearnersLast updated on May 26th, 2025
Divisibility Rule of 18
The divisibility rule is a way to find out whether a number is divisible by another number without using the division method. In real life, we can use the divisibility rule for quick math, dividing things evenly, and sorting things. In this topic, we will learn about the divisibility rule of 18.
What is the Divisibility Rule of 18?
The divisibility rule for 18 is a method by which we can find out if a number is divisible by 18 or not without using the division method. A number is divisible by 18 if it is divisible by both 2 and 9.
Check whether 234 is divisible by 18 with the divisibility rule.
Step 1: Check divisibility by 2. A number is divisible by 2 if its last digit is even. In 234, 4 is the last digit, which is even, so 234 is divisible by 2.
Step 2: Check divisibility by 9. A number is divisible by 9 if the sum of its digits is a multiple of 9. Add the digits of 234: 2 + 3 + 4 = 9. Since 9 is a multiple of 9, 234 is divisible by 9.
Step 3: Since 234 is divisible by both 2 and 9, it is divisible by 18.
Tips and Tricks for Divisibility Rule of 18
Learning the divisibility rule will help kids to master division. Let’s learn a few tips and tricks for the divisibility rule of 18.
- Know the multiples of 18: Memorize the multiples of 18 (18, 36, 54, 72, 90, etc.) to quickly check divisibility. If the result from the checks is a multiple of 18, then the number is divisible by 18.
- Use the sum of digits: If checking for 9, always remember to sum the digits and see if they form a multiple of 9.
- Repeat the process for large numbers: Students should keep repeating the divisibility process for both 2 and 9 until they reach a definitive conclusion.
- Use the division method to verify: Students can use the division method as a way to verify and crosscheck their results. This will help them to verify and also learn.
Common Mistakes and How to Avoid Them in Divisibility Rule of 18
The divisibility rule of 18 helps us to quickly check if the given number is divisible by 18, but common mistakes like calculation errors lead to incorrect calculations. Here we will understand some common mistakes that will help you to understand.
Mistake 1
Not checking divisibility by both 2 and 9.
Always ensure the number is divisible by both 2 and 9 to confirm divisibility by 18.
Divisibility Rule of 18 Examples
Problem 1
Is 324 divisible by 18?
Yes, 324 is divisible by 18.
Explanation
To check if 324 is divisible by 18, we need to verify divisibility by both 2 and 9.
1) Check divisibility by 2: The last digit is 4, which is even, so 324 is divisible by 2.
2) Check divisibility by 9: Add the digits 3 + 2 + 4 = 9, which is divisible by 9.
Since 324 is divisible by both 2 and 9, it is divisible by 18.
Problem 2
Check the divisibility rule of 18 for 612.
Yes, 612 is divisible by 18.
Explanation
To determine divisibility by 18, we check divisibility by 2 and 9.
1) Check divisibility by 2: The last digit is 2, which is even, so 612 is divisible by 2.
2) Check divisibility by 9: Sum the digits 6 + 1 + 2 = 9, which is divisible by 9.
Since 612 is divisible by both 2 and 9, it is divisible by 18.
Problem 3
Is 275 divisible by 18?
No, 275 is not divisible by 18.
Explanation
For divisibility by 18, the number must be divisible by both 2 and 9.
1) Check divisibility by 2: The last digit is 5, which is not even, so 275 is not divisible by 2.
2) Check divisibility by 9: Sum the digits 2 + 7 + 5 = 14, which is not divisible by 9.
Since 275 is not divisible by 2 and not divisible by 9, it is not divisible by 18.
Problem 4
Can 972 be divisible by 18 following the divisibility rule?
Yes, 972 is divisible by 18.
Explanation
We check divisibility by both 2 and 9.
1) Check divisibility by 2: The last digit is 2, which is even, so 972 is divisible by 2.
2) Check divisibility by 9: Sum the digits 9 + 7 + 2 = 18, which is divisible by 9.
Since 972 is divisible by both 2 and 9, it is divisible by 18.
Problem 5
Check the divisibility rule of 18 for 450.
No, 450 is not divisible by 18.
Explanation
We must check divisibility by 2 and 9.
1) Check divisibility by 2: The last digit is 0, which is even, so 450 is divisible by 2.
2) Check divisibility by 9: Sum the digits 4 + 5 + 0 = 9, which is divisible by 9.
Although 450 is divisible by 9, it must also be divisible by 2 and 9. Since it is divisible by both, my previous conclusion was incorrect. 450 is actually divisible by 18.
FAQs on Divisibility Rule of 18
1. What is the divisibility rule for 18?
2.How many numbers are there between 1 and 100 that are divisible by 18?
3.Is 54 divisible by 18?
4.What if I get 0 after summing the digits for 9?
5.Does the divisibility rule of 18 apply to all integers?
6.How can children in United States use numbers in everyday life to understand Divisibility Rule of 18?
7.What are some fun ways kids in United States can practice Divisibility Rule of 18 with numbers?
8.What role do numbers and Divisibility Rule of 18 play in helping children in United States develop problem-solving skills?
9.How can families in United States create number-rich environments to improve Divisibility Rule of 18 skills?
Important Glossaries for Divisibility Rule of 18
- Divisibility rule: The set of rules used to find out whether a number is divisible by another number or not.
- Multiples: The results we get after multiplying a number by an integer. For example, multiples of 18 are 18, 36, 54, etc.
- Integers: Numbers that include all whole numbers, negative numbers, and zero.
- Sum of digits: The total obtained by adding all the digits of a number.
- Even number: A number that is divisible by 2.
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Hiralee Lalitkumar Makwana
About the Author
Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.
Fun Fact
: She loves to read number jokes and games.
