481431 ÷ 21 
The aim is to understand the frequency of 21 in 481431.

Step 1:
4 divided by 21 is 0 with a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 4 and we're left with 4.
Include the next digit (8) from the dividend after 4, then repeat: 48 / 21

Let's proceed to step 2:
If we divide 48 by 21, we get 2 and a remainder of 6.
Write down 2 as next digit of the result. 
Result so far: 2.0
Subtracting 42 from 48 leaves us with 6.
Include the next digit (1) from the dividend after 6, then repeat: 61 / 21

On to step 3:
21 goes into 61 2 times with a remainder of 19.
Use 2 as the next digit of our solution. 
Result so far: 22.0
If we take 42 away from 61, we end up with 19.
Grab the next digit (4) from the dividend, add it to 19, then carry on: 194 / 21

On to step 4:
When dividing 194 by 21, we get 9 with a remainder of 5.
Record the quotient 9 as the next digit in the result. 
Result so far: 229.0
If we subtract 189 from 194, we get 5.
Grab the next digit (3) from the dividend, add it to 5, then carry on: 53 / 21

Moving on to step 5:
If we divide 53 by 21, we get 2 and a remainder of 11.
Write down 2 as next digit of the result. 
Result so far: 2292.0
If we subtract 42 from 53, we get 11.
Append the next digit (1) from the dividend to 11 and continue with: 111 / 21

Advancing to step 6:
21 can be fit into 111 5 times, resulting in a remainder of 6.
Record the quotient 5 as the next digit in the result. 
Result so far: 22925.0
The remainder is 6 after subtracting 105 from 111.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 7:
When dividing 60 by 21, we get 2 with a remainder of 18.
Put 2 as the next digit of the answer. 
Result so far: 22925.2
The remainder is 18 after subtracting 42 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Going ahead to step 8:
When dividing 180 by 21, we get 8 with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 22925.28
Subtracting 168 from 180 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Advancing to step 9:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 22925.285
Deduct 105 from 120 and we're left with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Advancing to step 10:
If we divide 150 by 21, we get 7 and a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 22925.2857
Deduct 147 from 150 and we're left with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Moving on to step 11:
21 goes into 30 1 times with a remainder of 9.
The next digit of our result is 1. 
Result so far: 22925.28571
If we subtract 21 from 30, we get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

On to step 12:
If we divide 90 by 21, we get 4 and a remainder of 6.
The next digit of our result is 4. 
Result so far: 22925.285714
The remainder is 6 after subtracting 84 from 90.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Advancing to step 13:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 22925.2857142
If we take 42 away from 60, we end up with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 14:
When dividing 180 by 21, we get 8 with a remainder of 12.
The number 8 becomes the next digit in our result. 
Result so far: 22925.28571428
If we take 168 away from 180, we end up with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

After the division, we end up with 22925.28571428 and a remainder of 1.2e-08.