We look at the division of 709645 by 81 
The aim is to understand the frequency of 81 in 709645.

On to step 1:
The number 81 fits into 7 0 times, leaving a remainder of 7.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 7, we get 7.
Take the next digit (0) from the dividend and append it to 7, then repeat: 70 / 81

On to step 2:
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: 0.0
If we take 0 away from 70, we end up with 70.
Fetch the next digit (9) from the dividend, attach it to 70 and continue: 709 / 81

Let's proceed to step 3:
The number 81 fits into 709 8 times, leaving a remainder of 61.
The number 8 becomes the next digit in our result. 
Result so far: 8.0
Subtracting 648 from 709 leaves us with 61.
Fetch the next digit (6) from the dividend, attach it to 61 and continue: 616 / 81

Step 4:
When dividing 616 by 81, we get 7 with a remainder of 49.
Use 7 as the next digit of our solution. 
Result so far: 87.0
Deduct 567 from 616 and we're left with 49.
Grab the next digit (4) from the dividend, add it to 49, then carry on: 494 / 81

Going ahead to step 5:
494 divided by 81 is 6 with a remainder of 8.
The next digit of our result is 6. 
Result so far: 876.0
The remainder is 8 after subtracting 486 from 494.
Grab the next digit (5) from the dividend, add it to 8, then carry on: 85 / 81

Moving on to step 6:
When dividing 85 by 81, we get 1 with a remainder of 4.
Write down 1 as next digit of the result. 
Result so far: 8761.0
Subtracting 81 from 85 leaves us with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Step 7:
The number 81 fits into 40 0 times, leaving a remainder of 40.
Use 0 as the next digit of our solution. 
Result so far: 8761.0
Subtract 0 from 40 to get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Moving on to step 8:
81 can be fit into 400 4 times, resulting in a remainder of 76.
Write down 4 as next digit of the result. 
Result so far: 8761.04
The remainder is 76 after subtracting 324 from 400.
Since there are no more digits in the dividend, we add a zero to the remainder making it 760, and continue the process.

On to step 9:
81 can be fit into 760 9 times, resulting in a remainder of 31.
The next digit of our result is 9. 
Result so far: 8761.049
Deduct 729 from 760 and we're left with 31.
Since there are no more digits in the dividend, we add a zero to the remainder making it 310, and continue the process.

Step 10:
The number 81 fits into 310 3 times, leaving a remainder of 67.
Put 3 as the next digit of the answer. 
Result so far: 8761.0493
Subtracting 243 from 310 leaves us with 67.
Since there are no more digits in the dividend, we add a zero to the remainder making it 670, and continue the process.

Advancing to step 11:
670 divided by 81 is 8 with a remainder of 22.
The next digit of our result is 8. 
Result so far: 8761.04938
Deduct 648 from 670 and we're left with 22.
Since there are no more digits in the dividend, we add a zero to the remainder making it 220, and continue the process.

Let's proceed to step 12:
When dividing 220 by 81, we get 2 with a remainder of 58.
The number 2 becomes the next digit in our result. 
Result so far: 8761.049382
The remainder is 58 after subtracting 162 from 220.
Since there are no more digits in the dividend, we add a zero to the remainder making it 580, and continue the process.

Step 13:
580 divided by 81 is 7 with a remainder of 13.
The next digit of our result is 7. 
Result so far: 8761.0493827
Subtracting 567 from 580 leaves us with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Moving on to step 14:
When dividing 130 by 81, we get 1 with a remainder of 49.
Write down 1 as next digit of the result. 
Result so far: 8761.04938271
If we subtract 81 from 130, we get 49.
Since there are no more digits in the dividend, we add a zero to the remainder making it 490, and continue the process.

The final outcome is 8761.04938271, with a leftover of 4.9e-08.