Let's divide 40353986 by 991
The aim is to understand the frequency of 991 in 40353986.

Going ahead to step 1:
When dividing 4 by 991, we get 0 with a remainder of 4.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 4 to get 4.
Grab the next digit (0) from the dividend, add it to 4, then carry on: 40 / 991

Moving on to step 2:
40 divided by 991 is 0 with a remainder of 40.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 40 leaves us with 40.
Bring next digit (3) of the dividend behind the 40 and repeat the process: 403 / 991

Going ahead to step 3:
991 can be fit into 403 0 times, resulting in a remainder of 403.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 403 leaves us with 403.
Grab the next digit (5) from the dividend, add it to 403, then carry on: 4035 / 991

Moving on to step 4:
991 goes into 4035 4 times with a remainder of 71.
The next digit of our result is 4. 
Result so far: 4.0
The remainder is 71 after subtracting 3964 from 4035.
Append the next digit (3) from the dividend to 71 and continue with: 713 / 991

Going ahead to step 5:
If we divide 713 by 991, we get 0 and a remainder of 713.
Use 0 as the next digit of our solution. 
Result so far: 40.0
Subtracting 0 from 713 leaves us with 713.
Bring next digit (9) of the dividend behind the 713 and repeat the process: 7139 / 991

Moving on to step 6:
If we divide 7139 by 991, we get 7 and a remainder of 202.
Use 7 as the next digit of our solution. 
Result so far: 407.0
Subtract 6937 from 7139 to get 202.
Append the next digit (8) from the dividend to 202 and continue with: 2028 / 991

Advancing to step 7:
When dividing 2028 by 991, we get 2 with a remainder of 46.
Write down 2 as next digit of the result. 
Result so far: 4072.0
Deduct 1982 from 2028 and we're left with 46.
Take the next digit (6) from the dividend and append it to 46, then repeat: 466 / 991

Moving on to step 8:
When dividing 466 by 991, we get 0 with a remainder of 466.
Record the quotient 0 as the next digit in the result. 
Result so far: 40720.0
If we take 0 away from 466, we end up with 466.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4660, and continue the process.

On to step 9:
991 goes into 4660 4 times with a remainder of 696.
Use 4 as the next digit of our solution. 
Result so far: 40720.4
The remainder is 696 after subtracting 3964 from 4660.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6960, and continue the process.

Let's proceed to step 10:
991 can be fit into 6960 7 times, resulting in a remainder of 23.
Record the quotient 7 as the next digit in the result. 
Result so far: 40720.47
If we take 6937 away from 6960, we end up with 23.
Since there are no more digits in the dividend, we add a zero to the remainder making it 230, and continue the process.

Advancing to step 11:
If we divide 230 by 991, we get 0 and a remainder of 230.
Write down 0 as next digit of the result. 
Result so far: 40720.47
If we subtract 0 from 230, we get 230.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2300, and continue the process.

Advancing to step 12:
2300 divided by 991 is 2 with a remainder of 318.
Put 2 as the next digit of the answer. 
Result so far: 40720.4702
Subtracting 1982 from 2300 leaves us with 318.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3180, and continue the process.

On to step 13:
3180 divided by 991 is 3 with a remainder of 207.
The number 3 becomes the next digit in our result. 
Result so far: 40720.47023
If we take 2973 away from 3180, we end up with 207.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2070, and continue the process.

Advancing to step 14:
991 can be fit into 2070 2 times, resulting in a remainder of 88.
Put 2 as the next digit of the answer. 
Result so far: 40720.470232
Subtracting 1982 from 2070 leaves us with 88.
Since there are no more digits in the dividend, we add a zero to the remainder making it 880, and continue the process.

Going ahead to step 15:
991 can be fit into 880 0 times, resulting in a remainder of 880.
The next digit of our result is 0. 
Result so far: 40720.470232
Deduct 0 from 880 and we're left with 880.
Since there are no more digits in the dividend, we add a zero to the remainder making it 8800, and continue the process.

Step 16:
991 goes into 8800 8 times with a remainder of 872.
The number 8 becomes the next digit in our result. 
Result so far: 40720.47023208
If we take 7928 away from 8800, we end up with 872.
Since there are no more digits in the dividend, we add a zero to the remainder making it 8720, and continue the process.

In conclusion, the division gives 40720.47023208 with a balance of 8.72e-07.