We look at the division of 687921 by 66 
The aim is to understand the frequency of 66 in 687921.

On to step 1:
66 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.
Include the next digit (8) from the dividend after 6, then repeat: 68 / 66

Advancing to step 2:
68 divided by 66 is 1 with a remainder of 2.
Write down 1 as next digit of the result. 
Result so far: 1.0
Subtract 66 from 68 to get 2.
Append the next digit (7) from the dividend to 2 and continue with: 27 / 66

Going ahead to step 3:
66 goes into 27 0 times with a remainder of 27.
Record the quotient 0 as the next digit in the result. 
Result so far: 10.0
If we take 0 away from 27, we end up with 27.
Take the next digit (9) from the dividend and append it to 27, then repeat: 279 / 66

Going ahead to step 4:
If we divide 279 by 66, we get 4 and a remainder of 15.
Use 4 as the next digit of our solution. 
Result so far: 104.0
Deduct 264 from 279 and we're left with 15.
Bring next digit (2) of the dividend behind the 15 and repeat the process: 152 / 66

Going ahead to step 5:
152 divided by 66 is 2 with a remainder of 20.
Write down 2 as next digit of the result. 
Result so far: 1042.0
If we take 132 away from 152, we end up with 20.
Bring next digit (1) of the dividend behind the 20 and repeat the process: 201 / 66

Step 6:
66 can be fit into 201 3 times, resulting in a remainder of 3.
The next digit of our result is 3. 
Result so far: 10423.0
If we subtract 198 from 201, we get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Step 7:
When dividing 30 by 66, we get 0 with a remainder of 30.
Use 0 as the next digit of our solution. 
Result so far: 10423.0
If we subtract 0 from 30, we get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Going ahead to step 8:
The number 66 fits into 300 4 times, leaving a remainder of 36.
The next digit of our result is 4. 
Result so far: 10423.04
Subtract 264 from 300 to get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Let's proceed to step 9:
66 can be fit into 360 5 times, resulting in a remainder of 30.
The number 5 becomes the next digit in our result. 
Result so far: 10423.045
If we subtract 330 from 360, we get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Step 10:
300 divided by 66 is 4 with a remainder of 36.
The next digit of our result is 4. 
Result so far: 10423.0454
The remainder is 36 after subtracting 264 from 300.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Advancing to step 11:
The number 66 fits into 360 5 times, leaving a remainder of 30.
Write down 5 as next digit of the result. 
Result so far: 10423.04545
Deduct 330 from 360 and we're left with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Let's proceed to step 12:
If we divide 300 by 66, we get 4 and a remainder of 36.
The number 4 becomes the next digit in our result. 
Result so far: 10423.045454
Subtract 264 from 300 to get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Moving on to step 13:
When dividing 360 by 66, we get 5 with a remainder of 30.
The number 5 becomes the next digit in our result. 
Result so far: 10423.0454545
Subtract 330 from 360 to get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Let's proceed to step 14:
66 can be fit into 300 4 times, resulting in a remainder of 36.
Record the quotient 4 as the next digit in the result. 
Result so far: 10423.04545454
Subtract 264 from 300 to get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

The final result is 10423.04545454 with a remainder of 3.6e-08.