We're dividing 113990 by 21 
The aim is to understand the frequency of 21 in 113990.

Going ahead to step 1:
21 can be fit into 1 0 times, resulting in a remainder of 1.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 1 after subtracting 0 from 1.
Append the next digit (1) from the dividend to 1 and continue with: 11 / 21

Let's proceed to step 2:
21 goes into 11 0 times with a remainder of 11.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 11 to get 11.
Fetch the next digit (3) from the dividend, attach it to 11 and continue: 113 / 21

On to step 3:
The number 21 fits into 113 5 times, leaving a remainder of 8.
Write down 5 as next digit of the result. 
Result so far: 5.0
Deduct 105 from 113 and we're left with 8.
Take the next digit (9) from the dividend and append it to 8, then repeat: 89 / 21

Going ahead to step 4:
If we divide 89 by 21, we get 4 and a remainder of 5.
Record the quotient 4 as the next digit in the result. 
Result so far: 54.0
Subtracting 84 from 89 leaves us with 5.
Append the next digit (9) from the dividend to 5 and continue with: 59 / 21

Let's proceed to step 5:
21 can be fit into 59 2 times, resulting in a remainder of 17.
The next digit of our result is 2. 
Result so far: 542.0
If we subtract 42 from 59, we get 17.
Grab the next digit (0) from the dividend, add it to 17, then carry on: 170 / 21

Moving on to step 6:
21 goes into 170 8 times with a remainder of 2.
Use 8 as the next digit of our solution. 
Result so far: 5428.0
Subtracting 168 from 170 leaves us with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 7:
If we divide 20 by 21, we get 0 and a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 5428.0
If we subtract 0 from 20, we get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 8:
21 goes into 200 9 times with a remainder of 11.
Put 9 as the next digit of the answer. 
Result so far: 5428.09
If we take 189 away from 200, we end up with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

On to step 9:
If we divide 110 by 21, we get 5 and a remainder of 5.
Record the quotient 5 as the next digit in the result. 
Result so far: 5428.095
The remainder is 5 after subtracting 105 from 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Advancing to step 10:
If we divide 50 by 21, we get 2 and a remainder of 8.
Use 2 as the next digit of our solution. 
Result so far: 5428.0952
If we take 42 away from 50, we end up with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 11:
80 divided by 21 is 3 with a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 5428.09523
Deduct 63 from 80 and we're left with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Moving on to step 12:
When dividing 170 by 21, we get 8 with a remainder of 2.
Write down 8 as next digit of the result. 
Result so far: 5428.095238
The remainder is 2 after subtracting 168 from 170.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 13:
21 can be fit into 20 0 times, resulting in a remainder of 20.
Write down 0 as next digit of the result. 
Result so far: 5428.095238
Subtracting 0 from 20 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Advancing to step 14:
200 divided by 21 is 9 with a remainder of 11.
The next digit of our result is 9. 
Result so far: 5428.09523809
Subtracting 189 from 200 leaves us with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

The final result is 5428.09523809 with a remainder of 1.1e-08.