Let's divide 521981 by 91
The aim is to understand the frequency of 91 in 521981.

On to step 1:
91 can be fit into 5 0 times, resulting in a remainder of 5.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 5, we get 5.
Include the next digit (2) from the dividend after 5, then repeat: 52 / 91

Advancing to step 2:
When dividing 52 by 91, we get 0 with a remainder of 52.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 52 after subtracting 0 from 52.
Append the next digit (1) from the dividend to 52 and continue with: 521 / 91

Moving on to step 3:
91 goes into 521 5 times with a remainder of 66.
Use 5 as the next digit of our solution. 
Result so far: 5.0
If we take 455 away from 521, we end up with 66.
Grab the next digit (9) from the dividend, add it to 66, then carry on: 669 / 91

Step 4:
When dividing 669 by 91, we get 7 with a remainder of 32.
Record the quotient 7 as the next digit in the result. 
Result so far: 57.0
The remainder is 32 after subtracting 637 from 669.
Bring next digit (8) of the dividend behind the 32 and repeat the process: 328 / 91

Step 5:
91 can be fit into 328 3 times, resulting in a remainder of 55.
Record the quotient 3 as the next digit in the result. 
Result so far: 573.0
Deduct 273 from 328 and we're left with 55.
Include the next digit (1) from the dividend after 55, then repeat: 551 / 91

On to step 6:
If we divide 551 by 91, we get 6 and a remainder of 5.
Record the quotient 6 as the next digit in the result. 
Result so far: 5736.0
Subtract 546 from 551 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Advancing to step 7:
When dividing 50 by 91, we get 0 with a remainder of 50.
The number 0 becomes the next digit in our result. 
Result so far: 5736.0
Deduct 0 from 50 and we're left with 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 500, and continue the process.

Let's proceed to step 8:
If we divide 500 by 91, we get 5 and a remainder of 45.
The next digit of our result is 5. 
Result so far: 5736.05
The remainder is 45 after subtracting 455 from 500.
Since there are no more digits in the dividend, we add a zero to the remainder making it 450, and continue the process.

Going ahead to step 9:
91 can be fit into 450 4 times, resulting in a remainder of 86.
The next digit of our result is 4. 
Result so far: 5736.054
The remainder is 86 after subtracting 364 from 450.
Since there are no more digits in the dividend, we add a zero to the remainder making it 860, and continue the process.

Step 10:
The number 91 fits into 860 9 times, leaving a remainder of 41.
Record the quotient 9 as the next digit in the result. 
Result so far: 5736.0549
If we take 819 away from 860, we end up with 41.
Since there are no more digits in the dividend, we add a zero to the remainder making it 410, and continue the process.

Going ahead to step 11:
91 goes into 410 4 times with a remainder of 46.
Use 4 as the next digit of our solution. 
Result so far: 5736.05494
The remainder is 46 after subtracting 364 from 410.
Since there are no more digits in the dividend, we add a zero to the remainder making it 460, and continue the process.

Step 12:
91 can be fit into 460 5 times, resulting in a remainder of 5.
Use 5 as the next digit of our solution. 
Result so far: 5736.054945
Subtracting 455 from 460 leaves us with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 13:
The number 91 fits into 50 0 times, leaving a remainder of 50.
Record the quotient 0 as the next digit in the result. 
Result so far: 5736.054945
Subtracting 0 from 50 leaves us with 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 500, and continue the process.

Advancing to step 14:
When dividing 500 by 91, we get 5 with a remainder of 45.
Write down 5 as next digit of the result. 
Result so far: 5736.05494505
Deduct 455 from 500 and we're left with 45.
Since there are no more digits in the dividend, we add a zero to the remainder making it 450, and continue the process.

In conclusion, the division gives 5736.05494505 with a balance of 4.5e-08.