We look at the division of 642413 by 91 
The aim is to understand the frequency of 91 in 642413.

Going ahead to step 1:
When dividing 6 by 91, we get 0 with a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 6 and we're left with 6.
Take the next digit (4) from the dividend and append it to 6, then repeat: 64 / 91

Moving on to step 2:
64 divided by 91 is 0 with a remainder of 64.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 64, we end up with 64.
Append the next digit (2) from the dividend to 64 and continue with: 642 / 91

Advancing to step 3:
When dividing 642 by 91, we get 7 with a remainder of 5.
Write down 7 as next digit of the result. 
Result so far: 7.0
Subtract 637 from 642 to get 5.
Fetch the next digit (4) from the dividend, attach it to 5 and continue: 54 / 91

On to step 4:
91 goes into 54 0 times with a remainder of 54.
Put 0 as the next digit of the answer. 
Result so far: 70.0
Deduct 0 from 54 and we're left with 54.
Take the next digit (1) from the dividend and append it to 54, then repeat: 541 / 91

On to step 5:
If we divide 541 by 91, we get 5 and a remainder of 86.
The next digit of our result is 5. 
Result so far: 705.0
If we take 455 away from 541, we end up with 86.
Take the next digit (3) from the dividend and append it to 86, then repeat: 863 / 91

On to step 6:
If we divide 863 by 91, we get 9 and a remainder of 44.
Use 9 as the next digit of our solution. 
Result so far: 7059.0
The remainder is 44 after subtracting 819 from 863.
Since there are no more digits in the dividend, we add a zero to the remainder making it 440, and continue the process.

Advancing to step 7:
The number 91 fits into 440 4 times, leaving a remainder of 76.
The number 4 becomes the next digit in our result. 
Result so far: 7059.4
Subtract 364 from 440 to get 76.
Since there are no more digits in the dividend, we add a zero to the remainder making it 760, and continue the process.

Moving on to step 8:
760 divided by 91 is 8 with a remainder of 32.
Use 8 as the next digit of our solution. 
Result so far: 7059.48
If we take 728 away from 760, we end up with 32.
Since there are no more digits in the dividend, we add a zero to the remainder making it 320, and continue the process.

Going ahead to step 9:
91 goes into 320 3 times with a remainder of 47.
The number 3 becomes the next digit in our result. 
Result so far: 7059.483
If we subtract 273 from 320, we 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.

Let's proceed to step 10:
470 divided by 91 is 5 with a remainder of 15.
The next digit of our result is 5. 
Result so far: 7059.4835
The remainder is 15 after subtracting 455 from 470.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Advancing to step 11:
91 goes into 150 1 times with a remainder of 59.
The next digit of our result is 1. 
Result so far: 7059.48351
Deduct 91 from 150 and we're left with 59.
Since there are no more digits in the dividend, we add a zero to the remainder making it 590, and continue the process.

Let's proceed to step 12:
If we divide 590 by 91, we get 6 and a remainder of 44.
Write down 6 as next digit of the result. 
Result so far: 7059.483516
Subtract 546 from 590 to get 44.
Since there are no more digits in the dividend, we add a zero to the remainder making it 440, and continue the process.

Advancing to step 13:
When dividing 440 by 91, we get 4 with a remainder of 76.
The number 4 becomes the next digit in our result. 
Result so far: 7059.4835164
Subtracting 364 from 440 leaves us with 76.
Since there are no more digits in the dividend, we add a zero to the remainder making it 760, and continue the process.

Step 14:
If we divide 760 by 91, we get 8 and a remainder of 32.
Write down 8 as next digit of the result. 
Result so far: 7059.48351648
If we take 728 away from 760, we end up with 32.
Since there are no more digits in the dividend, we add a zero to the remainder making it 320, and continue the process.

The final outcome is 7059.48351648, with a leftover of 3.2e-08.