We look at the division of 641188 by 81 
The aim is to understand the frequency of 81 in 641188.

Let's proceed to step 1:
6 divided by 81 is 0 with a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Grab the next digit (4) from the dividend, add it to 6, then carry on: 64 / 81

On to step 2:
The number 81 fits into 64 0 times, leaving a remainder of 64.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 64, we get 64.
Take the next digit (1) from the dividend and append it to 64, then repeat: 641 / 81

Let's proceed to step 3:
When dividing 641 by 81, we get 7 with a remainder of 74.
Use 7 as the next digit of our solution. 
Result so far: 7.0
Deduct 567 from 641 and we're left with 74.
Append the next digit (1) from the dividend to 74 and continue with: 741 / 81

Moving on to step 4:
If we divide 741 by 81, we get 9 and a remainder of 12.
The next digit of our result is 9. 
Result so far: 79.0
Deduct 729 from 741 and we're left with 12.
Append the next digit (8) from the dividend to 12 and continue with: 128 / 81

Going ahead to step 5:
81 can be fit into 128 1 times, resulting in a remainder of 47.
Write down 1 as next digit of the result. 
Result so far: 791.0
If we subtract 81 from 128, we get 47.
Grab the next digit (8) from the dividend, add it to 47, then carry on: 478 / 81

Moving on to step 6:
81 can be fit into 478 5 times, resulting in a remainder of 73.
Use 5 as the next digit of our solution. 
Result so far: 7915.0
If we take 405 away from 478, we end up with 73.
Since there are no more digits in the dividend, we add a zero to the remainder making it 730, and continue the process.

Let's proceed to step 7:
81 goes into 730 9 times with a remainder of 1.
Record the quotient 9 as the next digit in the result. 
Result so far: 7915.9
If we take 729 away from 730, we end up 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.

Step 8:
The number 81 fits into 10 0 times, leaving a remainder of 10.
Put 0 as the next digit of the answer. 
Result so far: 7915.9
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.

Advancing to step 9:
If we divide 100 by 81, we get 1 and a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 7915.901
If we take 81 away from 100, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Let's proceed to step 10:
190 divided by 81 is 2 with a remainder of 28.
The next digit of our result is 2. 
Result so far: 7915.9012
The remainder is 28 after subtracting 162 from 190.
Since there are no more digits in the dividend, we add a zero to the remainder making it 280, and continue the process.

On to step 11:
81 can be fit into 280 3 times, resulting in a remainder of 37.
The number 3 becomes the next digit in our result. 
Result so far: 7915.90123
The remainder is 37 after subtracting 243 from 280.
Since there are no more digits in the dividend, we add a zero to the remainder making it 370, and continue the process.

Advancing to step 12:
When dividing 370 by 81, we get 4 with a remainder of 46.
Put 4 as the next digit of the answer. 
Result so far: 7915.901234
If we subtract 324 from 370, we get 46.
Since there are no more digits in the dividend, we add a zero to the remainder making it 460, and continue the process.

Going ahead to step 13:
81 goes into 460 5 times with a remainder of 55.
Write down 5 as next digit of the result. 
Result so far: 7915.9012345
If we subtract 405 from 460, we get 55.
Since there are no more digits in the dividend, we add a zero to the remainder making it 550, and continue the process.

Advancing to step 14:
If we divide 550 by 81, we get 6 and a remainder of 64.
Use 6 as the next digit of our solution. 
Result so far: 7915.90123456
Subtract 486 from 550 to get 64.
Since there are no more digits in the dividend, we add a zero to the remainder making it 640, and continue the process.

The final outcome is 7915.90123456, with a leftover of 6.4e-08.