We're dividing 104878 by 21 
The aim is to understand the frequency of 21 in 104878.

Going ahead to step 1:
21 can be fit into 1 0 times, resulting in a remainder of 1.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 1 after subtracting 0 from 1.
Grab the next digit (0) from the dividend, add it to 1, then carry on: 10 / 21

On to step 2:
21 can be fit into 10 0 times, resulting in a remainder of 10.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 10 to get 10.
Include the next digit (4) from the dividend after 10, then repeat: 104 / 21

Let's proceed to step 3:
21 can be fit into 104 4 times, resulting in a remainder of 20.
The number 4 becomes the next digit in our result. 
Result so far: 4.0
The remainder is 20 after subtracting 84 from 104.
Grab the next digit (8) from the dividend, add it to 20, then carry on: 208 / 21

Moving on to step 4:
If we divide 208 by 21, we get 9 and a remainder of 19.
Write down 9 as next digit of the result. 
Result so far: 49.0
If we take 189 away from 208, we end up with 19.
Include the next digit (7) from the dividend after 19, then repeat: 197 / 21

Moving on to step 5:
21 goes into 197 9 times with a remainder of 8.
Use 9 as the next digit of our solution. 
Result so far: 499.0
Deduct 189 from 197 and we're left with 8.
Take the next digit (8) from the dividend and append it to 8, then repeat: 88 / 21

Moving on to step 6:
The number 21 fits into 88 4 times, leaving a remainder of 4.
The next digit of our result is 4. 
Result so far: 4994.0
The remainder is 4 after subtracting 84 from 88.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Step 7:
When dividing 40 by 21, we get 1 with a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 4994.1
Subtract 21 from 40 to get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Moving on to step 8:
When dividing 190 by 21, we get 9 with a remainder of 1.
Put 9 as the next digit of the answer. 
Result so far: 4994.19
Subtracting 189 from 190 leaves us with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Going ahead to step 9:
10 divided by 21 is 0 with a remainder of 10.
Use 0 as the next digit of our solution. 
Result so far: 4994.19
Subtract 0 from 10 to get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

On to step 10:
If we divide 100 by 21, we get 4 and a remainder of 16.
Put 4 as the next digit of the answer. 
Result so far: 4994.1904
If we subtract 84 from 100, we get 16.
Since there are no more digits in the dividend, we add a zero to the remainder making it 160, and continue the process.

Going ahead to step 11:
If we divide 160 by 21, we get 7 and a remainder of 13.
Use 7 as the next digit of our solution. 
Result so far: 4994.19047
If we take 147 away from 160, we end up with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Step 12:
When dividing 130 by 21, we get 6 with a remainder of 4.
The number 6 becomes the next digit in our result. 
Result so far: 4994.190476
Deduct 126 from 130 and we're left with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 13:
The number 21 fits into 40 1 times, leaving a remainder of 19.
The next digit of our result is 1. 
Result so far: 4994.1904761
Subtract 21 from 40 to get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

On to step 14:
190 divided by 21 is 9 with a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 4994.19047619
If we subtract 189 from 190, we get 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Our division results in 4994.19047619 with a remaining 1e-09.