66402038 ÷ 645 
The aim is to understand the frequency of 645 in 66402038.

Let's proceed to step 1:
645 can be fit into 6 0 times, resulting in a remainder of 6.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Grab the next digit (6) from the dividend, add it to 6, then carry on: 66 / 645

Let's proceed to step 2:
When dividing 66 by 645, we get 0 with a remainder of 66.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 66 leaves us with 66.
Include the next digit (4) from the dividend after 66, then repeat: 664 / 645

Moving on to step 3:
When dividing 664 by 645, we get 1 with a remainder of 19.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
The remainder is 19 after subtracting 645 from 664.
Bring next digit (0) of the dividend behind the 19 and repeat the process: 190 / 645

On to step 4:
When dividing 190 by 645, we get 0 with a remainder of 190.
The number 0 becomes the next digit in our result. 
Result so far: 10.0
If we subtract 0 from 190, we get 190.
Fetch the next digit (2) from the dividend, attach it to 190 and continue: 1902 / 645

Let's proceed to step 5:
1902 divided by 645 is 2 with a remainder of 612.
The number 2 becomes the next digit in our result. 
Result so far: 102.0
Deduct 1290 from 1902 and we're left with 612.
Take the next digit (0) from the dividend and append it to 612, then repeat: 6120 / 645

Let's proceed to step 6:
When dividing 6120 by 645, we get 9 with a remainder of 315.
Record the quotient 9 as the next digit in the result. 
Result so far: 1029.0
Subtract 5805 from 6120 to get 315.
Append the next digit (3) from the dividend to 315 and continue with: 3153 / 645

On to step 7:
If we divide 3153 by 645, we get 4 and a remainder of 573.
The number 4 becomes the next digit in our result. 
Result so far: 10294.0
The remainder is 573 after subtracting 2580 from 3153.
Include the next digit (8) from the dividend after 573, then repeat: 5738 / 645

Advancing to step 8:
645 goes into 5738 8 times with a remainder of 578.
Use 8 as the next digit of our solution. 
Result so far: 102948.0
Subtract 5160 from 5738 to get 578.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5780, and continue the process.

Step 9:
645 goes into 5780 8 times with a remainder of 620.
Use 8 as the next digit of our solution. 
Result so far: 102948.8
If we take 5160 away from 5780, we end up with 620.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6200, and continue the process.

Moving on to step 10:
The number 645 fits into 6200 9 times, leaving a remainder of 395.
The next digit of our result is 9. 
Result so far: 102948.89
Subtracting 5805 from 6200 leaves us with 395.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3950, and continue the process.

Going ahead to step 11:
The number 645 fits into 3950 6 times, leaving a remainder of 80.
Use 6 as the next digit of our solution. 
Result so far: 102948.896
Subtracting 3870 from 3950 leaves us with 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

On to step 12:
The number 645 fits into 800 1 times, leaving a remainder of 155.
Write down 1 as next digit of the result. 
Result so far: 102948.8961
The remainder is 155 after subtracting 645 from 800.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1550, and continue the process.

On to step 13:
645 goes into 1550 2 times with a remainder of 260.
Write down 2 as next digit of the result. 
Result so far: 102948.89612
If we subtract 1290 from 1550, we get 260.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2600, and continue the process.

Going ahead to step 14:
645 can be fit into 2600 4 times, resulting in a remainder of 20.
The number 4 becomes the next digit in our result. 
Result so far: 102948.896124
Subtract 2580 from 2600 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 15:
The number 645 fits into 200 0 times, leaving a remainder of 200.
Use 0 as the next digit of our solution. 
Result so far: 102948.896124
Deduct 0 from 200 and we're left with 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2000, and continue the process.

Step 16:
The number 645 fits into 2000 3 times, leaving a remainder of 65.
Record the quotient 3 as the next digit in the result. 
Result so far: 102948.89612403
The remainder is 65 after subtracting 1935 from 2000.
Since there are no more digits in the dividend, we add a zero to the remainder making it 650, and continue the process.

After the division, we end up with 102948.89612403 and a remainder of 6.5e-08.