There are many tricks which can be used by students to help them develop their skills in mathematics. Here are some quick ways to check the divisibility of any number.
Dividing by 2
All even numbers are divisible by 2. It is easy to identify an even number regardless of how large the value because all even numbers end in 0, 2, 4, 6 or 8.
Dividing by 3
Start by adding up all the digits in the number. Next, consider the sum and determine if the sum of the digits is divisible by 3. If the sum is divisible by 3, the original number is also divisible by 3.
Example: Is the value 12123 divisible by 3?
The sum of the digits is:
1 + 2 + 1 + 2 + 3 = 9
We know that the value 9 is divisible by 3, therefore we know that 12123 is also divisible by 3.
Dividing by 4
If the last two digits in your number are divisible by 4, then your number is also divisible by 4.
Example: Is the value 358912 divisible by 4?
The last two digits of this number are 12.
We know that 12 is divisible by 4, therefore we know that 358912 is divisible by 4.
Dividing by 5
If a number ends in a 5 or a 0 then the number is divisible by 5.
Example: Is 34665 divisible by 5?
Since the value ends in a 5 we know that the original number is divisible by 5.
Dividing by 6
If the number is divisible by 2 and 3 it is also divisible by 6.
Example: Is the value 2322 divisible by 6?
Since the value ends in a 2, it is even and thus divisible by 2.
The sum of the digits is:
2 + 3 + 2 + 2 = 9
Since the value 9 is divisible by 3, we know that the number 2322 is also divisible by 3.
Now we have that 2322 is divisible by 3 and 2, and can therefore conclude that 2322 is divisible by 6.
Dividing by 7
Start by taking the last digit in a number and doubling its value. Then, subtract this new value from the rest of the digits in your number. If the result is divisible by 7 then the original number is divisible by 7. Repeat the process as many times as needed for larger numbers.
Example: Is the value 357 divisible by 7?
The last digit is 7.
Doubling the final digit gives the value 14.
If we subtract 14 from the rest of the digits we get:
35 – 14 = 21
We know that 21 is divisible by 7 therefore we can conclude that 357 is divisible by 7.
Dividing by 8
If the last three digits of the value are divisible by 8, then the original number is also divisible by 8.
Example: Is the value 6008 divisible by 8?
The last 3 digits of the value are 008.
Since the value 8 is divisible by 8, we can conclude that 6008 is also divisible by 8.
Dividing by 9
Start by adding the digits in the number. If the sum of the digits in divisible by 9, then the number is also divisible by 9.
For example: Is the value 43785 divisible by 9?
First we find the sum of the digits:
4 + 3 + 7 + 8 + 5 = 27
We know that 27 is divisible by 9, therefore we can conclude that 43785 is also divisible by 9.
Dividing by 10
If the number ends in a 0, then it is divisible by 10.
Example: Is 345634530 divisible by 0?
Since the value ends in a 0, we know that it must be divisible by 10.
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This was written for you by Mia, one of the tutors with Test Prep Academy.