Divisibility Rule of 90

The divisibility rule for 90 is a method by which we can find out if a number is divisible by 90 or not without using the division method. To determine if a number is divisible by 90, it must be divisible by both 9 and 10. 
 

Let's check whether 450 is divisible by 90 with the divisibility rule:

Step 1: Check divisibility by 10. A number is divisible by 10 if its last digit is 0. In 450, the last digit is 0, so it is divisible by 10.

Step 2: Check divisibility by 9. A number is divisible by 9 if the sum of its digits is divisible by 9. The sum of the digits in 450 is 4 + 5 + 0 = 9, which is divisible by 9.

Step 3: Since 450 is divisible by both 10 and 9, it is divisible by 90.
 

Learning the divisibility rule will help kids master division. Let’s learn a few tips and tricks for the divisibility rule of 90.
 

• Know the multiples of 90: Memorize the multiples of 90 (90, 180, 270, 360, etc.) to quickly check divisibility. If both conditions for divisibility by 9 and 10 are met, the number is divisible by 90.
   
• Use the sum of digits for 9: Always calculate the sum of the digits of the number to check divisibility by 9. Ensure the result is a multiple of 9.
   
• Repeat for large numbers: If needed, repeat the process to simplify or verify calculations. 
   
• 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.
   

• Divisibility rule: The set of rules used to find out whether a number is divisible by another number without direct division. For example, a number is divisible by 10 if it ends in 0.
   
• Multiples: Multiples are the results we get after multiplying a number by an integer. For example, multiples of 90 are 90, 180, 270, etc.
   
• Sum of digits: The total obtained by adding all the digits of a number. Used to determine divisibility by 9.
   
• Integers: Integers are the numbers that include all whole numbers, negative numbers, and zero.
   
• Last digit check: The process of examining the last digit of a number to determine divisibility by 10.