9916043 ÷ 645 
The aim is to understand the frequency of 645 in 9916043.

Step 1:
645 goes into 9 0 times with a remainder of 9.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 9 and we're left with 9.
Include the next digit (9) from the dividend after 9, then repeat: 99 / 645

Step 2:
99 divided by 645 is 0 with a remainder of 99.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 99 and we're left with 99.
Take the next digit (1) from the dividend and append it to 99, then repeat: 991 / 645

Advancing to step 3:
If we divide 991 by 645, we get 1 and a remainder of 346.
Put 1 as the next digit of the answer. 
Result so far: 1.0
If we take 645 away from 991, we end up with 346.
Fetch the next digit (6) from the dividend, attach it to 346 and continue: 3466 / 645

Let's proceed to step 4:
The number 645 fits into 3466 5 times, leaving a remainder of 241.
Use 5 as the next digit of our solution. 
Result so far: 15.0
Deduct 3225 from 3466 and we're left with 241.
Append the next digit (0) from the dividend to 241 and continue with: 2410 / 645

Moving on to step 5:
The number 645 fits into 2410 3 times, leaving a remainder of 475.
Write down 3 as next digit of the result. 
Result so far: 153.0
If we subtract 1935 from 2410, we get 475.
Append the next digit (4) from the dividend to 475 and continue with: 4754 / 645

Going ahead to step 6:
The number 645 fits into 4754 7 times, leaving a remainder of 239.
Write down 7 as next digit of the result. 
Result so far: 1537.0
Subtract 4515 from 4754 to get 239.
Append the next digit (3) from the dividend to 239 and continue with: 2393 / 645

Step 7:
2393 divided by 645 is 3 with a remainder of 458.
Record the quotient 3 as the next digit in the result. 
Result so far: 15373.0
If we subtract 1935 from 2393, we get 458.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4580, and continue the process.

Going ahead to step 8:
The number 645 fits into 4580 7 times, leaving a remainder of 65.
Put 7 as the next digit of the answer. 
Result so far: 15373.7
Subtract 4515 from 4580 to get 65.
Since there are no more digits in the dividend, we add a zero to the remainder making it 650, and continue the process.

Advancing to step 9:
645 can be fit into 650 1 times, resulting in a remainder of 5.
Use 1 as the next digit of our solution. 
Result so far: 15373.71
The remainder is 5 after subtracting 645 from 650.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

On to step 10:
645 can be fit into 50 0 times, resulting in a remainder of 50.
Use 0 as the next digit of our solution. 
Result so far: 15373.71
If we subtract 0 from 50, we get 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 500, and continue the process.

Moving on to step 11:
The number 645 fits into 500 0 times, leaving a remainder of 500.
The number 0 becomes the next digit in our result. 
Result so far: 15373.71
Subtract 0 from 500 to get 500.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5000, and continue the process.

The quotient of the division is 15373.71, and the remainder is 0.005.