81503409 ÷ 991 
The aim is to understand the frequency of 991 in 81503409.

Advancing to step 1:
991 goes into 8 0 times with a remainder of 8.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 8 to get 8.
Grab the next digit (1) from the dividend, add it to 8, then carry on: 81 / 991

Moving on to step 2:
991 goes into 81 0 times with a remainder of 81.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 81, we end up with 81.
Append the next digit (5) from the dividend to 81 and continue with: 815 / 991

Moving on to step 3:
991 goes into 815 0 times with a remainder of 815.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 815 to get 815.
Append the next digit (0) from the dividend to 815 and continue with: 8150 / 991

Moving on to step 4:
If we divide 8150 by 991, we get 8 and a remainder of 222.
Put 8 as the next digit of the answer. 
Result so far: 8.0
Subtract 7928 from 8150 to get 222.
Take the next digit (3) from the dividend and append it to 222, then repeat: 2223 / 991

On to step 5:
If we divide 2223 by 991, we get 2 and a remainder of 241.
Use 2 as the next digit of our solution. 
Result so far: 82.0
Subtracting 1982 from 2223 leaves us with 241.
Bring next digit (4) of the dividend behind the 241 and repeat the process: 2414 / 991

Step 6:
The number 991 fits into 2414 2 times, leaving a remainder of 432.
Write down 2 as next digit of the result. 
Result so far: 822.0
Subtract 1982 from 2414 to get 432.
Bring next digit (0) of the dividend behind the 432 and repeat the process: 4320 / 991

Moving on to step 7:
4320 divided by 991 is 4 with a remainder of 356.
The next digit of our result is 4. 
Result so far: 8224.0
If we take 3964 away from 4320, we end up with 356.
Bring next digit (9) of the dividend behind the 356 and repeat the process: 3569 / 991

Moving on to step 8:
If we divide 3569 by 991, we get 3 and a remainder of 596.
Record the quotient 3 as the next digit in the result. 
Result so far: 82243.0
Subtract 2973 from 3569 to get 596.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5960, and continue the process.

Moving on to step 9:
If we divide 5960 by 991, we get 6 and a remainder of 14.
Use 6 as the next digit of our solution. 
Result so far: 82243.6
Deduct 5946 from 5960 and we're left with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

On to step 10:
991 goes into 140 0 times with a remainder of 140.
The number 0 becomes the next digit in our result. 
Result so far: 82243.6
The remainder is 140 after subtracting 0 from 140.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1400, and continue the process.

Advancing to step 11:
When dividing 1400 by 991, we get 1 with a remainder of 409.
Put 1 as the next digit of the answer. 
Result so far: 82243.601
If we take 991 away from 1400, we end up with 409.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4090, and continue the process.

Step 12:
When dividing 4090 by 991, we get 4 with a remainder of 126.
Use 4 as the next digit of our solution. 
Result so far: 82243.6014
Subtracting 3964 from 4090 leaves us with 126.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1260, and continue the process.

Moving on to step 13:
If we divide 1260 by 991, we get 1 and a remainder of 269.
Record the quotient 1 as the next digit in the result. 
Result so far: 82243.60141
If we subtract 991 from 1260, we get 269.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2690, and continue the process.

Advancing to step 14:
When dividing 2690 by 991, we get 2 with a remainder of 708.
Use 2 as the next digit of our solution. 
Result so far: 82243.601412
If we subtract 1982 from 2690, we get 708.
Since there are no more digits in the dividend, we add a zero to the remainder making it 7080, and continue the process.

Step 15:
7080 divided by 991 is 7 with a remainder of 143.
Write down 7 as next digit of the result. 
Result so far: 82243.6014127
If we take 6937 away from 7080, we end up with 143.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1430, and continue the process.

Advancing to step 16:
991 goes into 1430 1 times with a remainder of 439.
Record the quotient 1 as the next digit in the result. 
Result so far: 82243.60141271
The remainder is 439 after subtracting 991 from 1430.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4390, and continue the process.

The final outcome is 82243.60141271, with a leftover of 4.39e-07.