We look at the division of 816392 by 81 
The aim is to understand the frequency of 81 in 816392.

Advancing to step 1:
When dividing 8 by 81, we get 0 with a remainder of 8.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 8 and we're left with 8.
Grab the next digit (1) from the dividend, add it to 8, then carry on: 81 / 81

Advancing to step 2:
81 can be fit into 81 1 times, resulting in a remainder of 0.
Use 1 as the next digit of our solution. 
Result so far: 1.0
Deduct 81 from 81 and we're left with 0.
Fetch the next digit (6) from the dividend, attach it to 0 and continue: 6 / 81

Moving on to step 3:
When dividing 6 by 81, we get 0 with a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 10.0
If we subtract 0 from 6, we get 6.
Append the next digit (3) from the dividend to 6 and continue with: 63 / 81

Moving on to step 4:
If we divide 63 by 81, we get 0 and a remainder of 63.
The number 0 becomes the next digit in our result. 
Result so far: 100.0
The remainder is 63 after subtracting 0 from 63.
Include the next digit (9) from the dividend after 63, then repeat: 639 / 81

On to step 5:
The number 81 fits into 639 7 times, leaving a remainder of 72.
Record the quotient 7 as the next digit in the result. 
Result so far: 1007.0
Subtracting 567 from 639 leaves us with 72.
Fetch the next digit (2) from the dividend, attach it to 72 and continue: 722 / 81

On to step 6:
722 divided by 81 is 8 with a remainder of 74.
Record the quotient 8 as the next digit in the result. 
Result so far: 10078.0
If we subtract 648 from 722, we get 74.
Since there are no more digits in the dividend, we add a zero to the remainder making it 740, and continue the process.

On to step 7:
740 divided by 81 is 9 with a remainder of 11.
The number 9 becomes the next digit in our result. 
Result so far: 10078.9
Deduct 729 from 740 and we're left 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.

Let's proceed to step 8:
If we divide 110 by 81, we get 1 and a remainder of 29.
Put 1 as the next digit of the answer. 
Result so far: 10078.91
Deduct 81 from 110 and we're left with 29.
Since there are no more digits in the dividend, we add a zero to the remainder making it 290, and continue the process.

Moving on to step 9:
When dividing 290 by 81, we get 3 with a remainder of 47.
Record the quotient 3 as the next digit in the result. 
Result so far: 10078.913
Subtract 243 from 290 to get 47.
Since there are no more digits in the dividend, we add a zero to the remainder making it 470, and continue the process.

Moving on to step 10:
470 divided by 81 is 5 with a remainder of 65.
Put 5 as the next digit of the answer. 
Result so far: 10078.9135
Deduct 405 from 470 and we're left with 65.
Since there are no more digits in the dividend, we add a zero to the remainder making it 650, and continue the process.

Going ahead to step 11:
When dividing 650 by 81, we get 8 with a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 10078.91358
The remainder is 2 after subtracting 648 from 650.
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 12:
The number 81 fits into 20 0 times, leaving a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 10078.91358
Deduct 0 from 20 and we're left 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.

Moving on to step 13:
81 goes into 200 2 times with a remainder of 38.
Write down 2 as next digit of the result. 
Result so far: 10078.9135802
Subtracting 162 from 200 leaves us with 38.
Since there are no more digits in the dividend, we add a zero to the remainder making it 380, and continue the process.

Step 14:
81 can be fit into 380 4 times, resulting in a remainder of 56.
Write down 4 as next digit of the result. 
Result so far: 10078.91358024
If we subtract 324 from 380, we get 56.
Since there are no more digits in the dividend, we add a zero to the remainder making it 560, and continue the process.

The final outcome is 10078.91358024, with a leftover of 5.6e-08.