99619864 ÷ 645 
The aim is to understand the frequency of 645 in 99619864.

Step 1:
The number 645 fits into 9 0 times, leaving a remainder of 9.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 9 after subtracting 0 from 9.
Take the next digit (9) from the dividend and append it to 9, then repeat: 99 / 645

Going ahead to step 2:
The number 645 fits into 99 0 times, leaving a remainder of 99.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 99 to get 99.
Bring next digit (6) of the dividend behind the 99 and repeat the process: 996 / 645

Moving on to step 3:
645 can be fit into 996 1 times, resulting in a remainder of 351.
Write down 1 as next digit of the result. 
Result so far: 1.0
Subtracting 645 from 996 leaves us with 351.
Take the next digit (1) from the dividend and append it to 351, then repeat: 3511 / 645

Step 4:
The number 645 fits into 3511 5 times, leaving a remainder of 286.
The next digit of our result is 5. 
Result so far: 15.0
If we take 3225 away from 3511, we end up with 286.
Include the next digit (9) from the dividend after 286, then repeat: 2869 / 645

Let's proceed to step 5:
645 can be fit into 2869 4 times, resulting in a remainder of 289.
The next digit of our result is 4. 
Result so far: 154.0
If we take 2580 away from 2869, we end up with 289.
Bring next digit (8) of the dividend behind the 289 and repeat the process: 2898 / 645

On to step 6:
When dividing 2898 by 645, we get 4 with a remainder of 318.
Use 4 as the next digit of our solution. 
Result so far: 1544.0
Deduct 2580 from 2898 and we're left with 318.
Append the next digit (6) from the dividend to 318 and continue with: 3186 / 645

Going ahead to step 7:
3186 divided by 645 is 4 with a remainder of 606.
Use 4 as the next digit of our solution. 
Result so far: 15444.0
If we take 2580 away from 3186, we end up with 606.
Include the next digit (4) from the dividend after 606, then repeat: 6064 / 645

On to step 8:
645 goes into 6064 9 times with a remainder of 259.
The next digit of our result is 9. 
Result so far: 154449.0
If we subtract 5805 from 6064, we get 259.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2590, and continue the process.

Step 9:
If we divide 2590 by 645, we get 4 and a remainder of 10.
Record the quotient 4 as the next digit in the result. 
Result so far: 154449.4
If we take 2580 away from 2590, we end up with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Moving on to step 10:
100 divided by 645 is 0 with a remainder of 100.
Use 0 as the next digit of our solution. 
Result so far: 154449.4
Subtract 0 from 100 to get 100.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1000, and continue the process.

Advancing to step 11:
If we divide 1000 by 645, we get 1 and a remainder of 355.
The next digit of our result is 1. 
Result so far: 154449.401
Subtracting 645 from 1000 leaves us with 355.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3550, and continue the process.

Going ahead to step 12:
3550 divided by 645 is 5 with a remainder of 325.
Put 5 as the next digit of the answer. 
Result so far: 154449.4015
Deduct 3225 from 3550 and we're left with 325.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3250, and continue the process.

Going ahead to step 13:
3250 divided by 645 is 5 with a remainder of 25.
Put 5 as the next digit of the answer. 
Result so far: 154449.40155
Deduct 3225 from 3250 and we're left with 25.
Since there are no more digits in the dividend, we add a zero to the remainder making it 250, and continue the process.

Our division results in 154449.40155 with a remaining 2.5e-05.