We look at the division of 171381 by 66 
The aim is to understand the frequency of 66 in 171381.

On to step 1:
The number 66 fits into 1 0 times, leaving a remainder of 1.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 1 leaves us with 1.
Include the next digit (7) from the dividend after 1, then repeat: 17 / 66

Going ahead to step 2:
If we divide 17 by 66, we get 0 and a remainder of 17.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 17 and we're left with 17.
Append the next digit (1) from the dividend to 17 and continue with: 171 / 66

Step 3:
The number 66 fits into 171 2 times, leaving a remainder of 39.
Write down 2 as next digit of the result. 
Result so far: 2.0
If we subtract 132 from 171, we get 39.
Include the next digit (3) from the dividend after 39, then repeat: 393 / 66

On to step 4:
If we divide 393 by 66, we get 5 and a remainder of 63.
Write down 5 as next digit of the result. 
Result so far: 25.0
Subtract 330 from 393 to get 63.
Include the next digit (8) from the dividend after 63, then repeat: 638 / 66

Let's proceed to step 5:
66 goes into 638 9 times with a remainder of 44.
The next digit of our result is 9. 
Result so far: 259.0
Subtracting 594 from 638 leaves us with 44.
Bring next digit (1) of the dividend behind the 44 and repeat the process: 441 / 66

Moving on to step 6:
When dividing 441 by 66, we get 6 with a remainder of 45.
Record the quotient 6 as the next digit in the result. 
Result so far: 2596.0
If we take 396 away from 441, we end up with 45.
Since there are no more digits in the dividend, we add a zero to the remainder making it 450, and continue the process.

Moving on to step 7:
The number 66 fits into 450 6 times, leaving a remainder of 54.
Put 6 as the next digit of the answer. 
Result so far: 2596.6
If we take 396 away from 450, we end up with 54.
Since there are no more digits in the dividend, we add a zero to the remainder making it 540, and continue the process.

Advancing to step 8:
If we divide 540 by 66, we get 8 and a remainder of 12.
Write down 8 as next digit of the result. 
Result so far: 2596.68
Subtracting 528 from 540 leaves us with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 9:
66 can be fit into 120 1 times, resulting in a remainder of 54.
Write down 1 as next digit of the result. 
Result so far: 2596.681
Deduct 66 from 120 and we're left with 54.
Since there are no more digits in the dividend, we add a zero to the remainder making it 540, and continue the process.

On to step 10:
The number 66 fits into 540 8 times, leaving a remainder of 12.
Record the quotient 8 as the next digit in the result. 
Result so far: 2596.6818
If we subtract 528 from 540, we get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

On to step 11:
The number 66 fits into 120 1 times, leaving a remainder of 54.
The number 1 becomes the next digit in our result. 
Result so far: 2596.68181
Subtract 66 from 120 to get 54.
Since there are no more digits in the dividend, we add a zero to the remainder making it 540, and continue the process.

On to step 12:
When dividing 540 by 66, we get 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 2596.681818
If we subtract 528 from 540, we get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Step 13:
120 divided by 66 is 1 with a remainder of 54.
Use 1 as the next digit of our solution. 
Result so far: 2596.6818181
Deduct 66 from 120 and we're left with 54.
Since there are no more digits in the dividend, we add a zero to the remainder making it 540, and continue the process.

Moving on to step 14:
66 can be fit into 540 8 times, resulting in a remainder of 12.
Write down 8 as next digit of the result. 
Result so far: 2596.68181818
Deduct 528 from 540 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Our division results in 2596.68181818 with a remaining 1.2e-08.