We look at the division of 413541 by 81 
The aim is to understand the frequency of 81 in 413541.

Going ahead to step 1:
81 can be fit into 4 0 times, resulting in a remainder of 4.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 4 and we're left with 4.
Grab the next digit (1) from the dividend, add it to 4, then carry on: 41 / 81

On to step 2:
If we divide 41 by 81, we get 0 and a remainder of 41.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtract 0 from 41 to get 41.
Bring next digit (3) of the dividend behind the 41 and repeat the process: 413 / 81

Going ahead to step 3:
413 divided by 81 is 5 with a remainder of 8.
Write down 5 as next digit of the result. 
Result so far: 5.0
Subtracting 405 from 413 leaves us with 8.
Append the next digit (5) from the dividend to 8 and continue with: 85 / 81

Moving on to step 4:
When dividing 85 by 81, we get 1 with a remainder of 4.
Put 1 as the next digit of the answer. 
Result so far: 51.0
Deduct 81 from 85 and we're left with 4.
Include the next digit (4) from the dividend after 4, then repeat: 44 / 81

On to step 5:
81 can be fit into 44 0 times, resulting in a remainder of 44.
Record the quotient 0 as the next digit in the result. 
Result so far: 510.0
If we take 0 away from 44, we end up with 44.
Include the next digit (1) from the dividend after 44, then repeat: 441 / 81

Moving on to step 6:
When dividing 441 by 81, we get 5 with a remainder of 36.
Write down 5 as next digit of the result. 
Result so far: 5105.0
If we take 405 away from 441, we end up with 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

On to step 7:
81 goes into 360 4 times with a remainder of 36.
Record the quotient 4 as the next digit in the result. 
Result so far: 5105.4
Subtracting 324 from 360 leaves us with 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Going ahead to step 8:
81 can be fit into 360 4 times, resulting in a remainder of 36.
The next digit of our result is 4. 
Result so far: 5105.44
If we subtract 324 from 360, we get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

The final result is 5105.44 with a remainder of 0.036.