We look at the division of 46509593 by 646 
The aim is to understand the frequency of 646 in 46509593.

On to step 1:
If we divide 4 by 646, we get 0 and a remainder of 4.
The next digit of our result is 0. 
Result so far: 0.0
The remainder is 4 after subtracting 0 from 4.
Include the next digit (6) from the dividend after 4, then repeat: 46 / 646

Step 2:
When dividing 46 by 646, we get 0 with a remainder of 46.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 46 after subtracting 0 from 46.
Fetch the next digit (5) from the dividend, attach it to 46 and continue: 465 / 646

Let's proceed to step 3:
When dividing 465 by 646, we get 0 with a remainder of 465.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 465 after subtracting 0 from 465.
Include the next digit (0) from the dividend after 465, then repeat: 4650 / 646

Moving on to step 4:
The number 646 fits into 4650 7 times, leaving a remainder of 128.
Use 7 as the next digit of our solution. 
Result so far: 7.0
Deduct 4522 from 4650 and we're left with 128.
Grab the next digit (9) from the dividend, add it to 128, then carry on: 1289 / 646

Moving on to step 5:
1289 divided by 646 is 1 with a remainder of 643.
Record the quotient 1 as the next digit in the result. 
Result so far: 71.0
Subtract 646 from 1289 to get 643.
Bring next digit (5) of the dividend behind the 643 and repeat the process: 6435 / 646

Step 6:
646 can be fit into 6435 9 times, resulting in a remainder of 621.
Put 9 as the next digit of the answer. 
Result so far: 719.0
If we take 5814 away from 6435, we end up with 621.
Append the next digit (9) from the dividend to 621 and continue with: 6219 / 646

Let's proceed to step 7:
646 goes into 6219 9 times with a remainder of 405.
Put 9 as the next digit of the answer. 
Result so far: 7199.0
Subtract 5814 from 6219 to get 405.
Take the next digit (3) from the dividend and append it to 405, then repeat: 4053 / 646

Advancing to step 8:
646 can be fit into 4053 6 times, resulting in a remainder of 177.
The number 6 becomes the next digit in our result. 
Result so far: 71996.0
Subtract 3876 from 4053 to get 177.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1770, and continue the process.

Going ahead to step 9:
646 can be fit into 1770 2 times, resulting in a remainder of 478.
Write down 2 as next digit of the result. 
Result so far: 71996.2
Subtract 1292 from 1770 to get 478.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4780, and continue the process.

Step 10:
When dividing 4780 by 646, we get 7 with a remainder of 258.
Write down 7 as next digit of the result. 
Result so far: 71996.27
Subtract 4522 from 4780 to get 258.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2580, and continue the process.

Advancing to step 11:
The number 646 fits into 2580 3 times, leaving a remainder of 642.
Use 3 as the next digit of our solution. 
Result so far: 71996.273
Subtracting 1938 from 2580 leaves us with 642.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6420, and continue the process.

Advancing to step 12:
646 goes into 6420 9 times with a remainder of 606.
Put 9 as the next digit of the answer. 
Result so far: 71996.2739
If we take 5814 away from 6420, we end up with 606.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6060, and continue the process.

Advancing to step 13:
6060 divided by 646 is 9 with a remainder of 246.
The number 9 becomes the next digit in our result. 
Result so far: 71996.27399
If we take 5814 away from 6060, we end up with 246.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2460, and continue the process.

After the division, we end up with 71996.27399 and a remainder of 0.000246.