91921678 divided by 81 
The aim is to understand the frequency of 81 in 91921678.

Let's proceed to step 1:
9 divided by 81 is 0 with a remainder of 9.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 9 after subtracting 0 from 9.
Grab the next digit (1) from the dividend, add it to 9, then carry on: 91 / 81

Let's proceed to step 2:
If we divide 91 by 81, we get 1 and a remainder of 10.
The next digit of our result is 1. 
Result so far: 1.0
Subtract 81 from 91 to get 10.
Fetch the next digit (9) from the dividend, attach it to 10 and continue: 109 / 81

Let's proceed to step 3:
If we divide 109 by 81, we get 1 and a remainder of 28.
The next digit of our result is 1. 
Result so far: 11.0
Deduct 81 from 109 and we're left with 28.
Bring next digit (2) of the dividend behind the 28 and repeat the process: 282 / 81

Moving on to step 4:
If we divide 282 by 81, we get 3 and a remainder of 39.
Put 3 as the next digit of the answer. 
Result so far: 113.0
Deduct 243 from 282 and we're left with 39.
Bring next digit (1) of the dividend behind the 39 and repeat the process: 391 / 81

Advancing to step 5:
81 goes into 391 4 times with a remainder of 67.
Write down 4 as next digit of the result. 
Result so far: 1134.0
The remainder is 67 after subtracting 324 from 391.
Grab the next digit (6) from the dividend, add it to 67, then carry on: 676 / 81

Step 6:
676 divided by 81 is 8 with a remainder of 28.
Use 8 as the next digit of our solution. 
Result so far: 11348.0
If we subtract 648 from 676, we get 28.
Grab the next digit (7) from the dividend, add it to 28, then carry on: 287 / 81

Step 7:
The number 81 fits into 287 3 times, leaving a remainder of 44.
The number 3 becomes the next digit in our result. 
Result so far: 113483.0
If we take 243 away from 287, we end up with 44.
Bring next digit (8) of the dividend behind the 44 and repeat the process: 448 / 81

Let's proceed to step 8:
When dividing 448 by 81, we get 5 with a remainder of 43.
Record the quotient 5 as the next digit in the result. 
Result so far: 1134835.0
Subtracting 405 from 448 leaves us with 43.
Since there are no more digits in the dividend, we add a zero to the remainder making it 430, and continue the process.

Step 9:
If we divide 430 by 81, we get 5 and a remainder of 25.
Record the quotient 5 as the next digit in the result. 
Result so far: 1134835.5
Deduct 405 from 430 and we're left with 25.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

Step 10:
250 divided by 81 is 3 with a remainder of 7.
Use 3 as the next digit of our solution. 
Result so far: 1134835.53
If we subtract 243 from 250, we get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Advancing to step 11:
If we divide 70 by 81, we get 0 and a remainder of 70.
The next digit of our result is 0. 
Result so far: 1134835.53
If we subtract 0 from 70, we get 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 700, and continue the process.

Moving on to step 12:
The number 81 fits into 700 8 times, leaving a remainder of 52.
Record the quotient 8 as the next digit in the result. 
Result so far: 1134835.5308
Subtract 648 from 700 to get 52.
Since there are no more digits in the dividend, we add a zero to the remainder making it 520, and continue the process.

Going ahead to step 13:
81 can be fit into 520 6 times, resulting in a remainder of 34.
Put 6 as the next digit of the answer. 
Result so far: 1134835.53086
Subtracting 486 from 520 leaves us with 34.
Since there are no more digits in the dividend, we add a zero to the remainder making it 340, and continue the process.

Going ahead to step 14:
81 can be fit into 340 4 times, resulting in a remainder of 16.
Use 4 as the next digit of our solution. 
Result so far: 1134835.530864
If we subtract 324 from 340, 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.

Moving on to step 15:
The number 81 fits into 160 1 times, leaving a remainder of 79.
Write down 1 as next digit of the result. 
Result so far: 1134835.5308641
Subtracting 81 from 160 leaves us with 79.
Since there are no more digits in the dividend, we add a zero to the remainder making it 790, and continue the process.

Moving on to step 16:
If we divide 790 by 81, we get 9 and a remainder of 61.
Use 9 as the next digit of our solution. 
Result so far: 1134835.53086419
The remainder is 61 after subtracting 729 from 790.
Since there are no more digits in the dividend, we add a zero to the remainder making it 610, and continue the process.

The final result is 1134835.53086419 with a remainder of 6.1e-08.